Annona muricata: Comprehensive Review on the Ethnomedicinal, Phytochemistry, and Pharmacological Aspects Focusing on Antidiabetic Properties

Plants have played an important role over the centuries in providing products that have been used to help combat ailments and diseases. Many products originating from fresh, dried-plant materials, or extracts are utilized as community remedies in traditional practices or even in modern medicine. The Annonaceae family contains different types of bioactive chemical properties, such as alkaloids, acetogenins, flavonoids, terpenes, and essential oil, meaning the plants in this family are potential therapeutic agents. Belonging to the Annonaceae family, Annona muricata Linn. has recently attracted the attention of scientists for its medicinal value. It has been utilized as a medicinal remedy since ancient times to treat and improve various diseases, for example, diabetes mellitus, hypertension, cancer, and bacterial infections. This review, therefore, highlights the important characteristic and therapeutic effect of A. muricata along with future perspectives on its hypoglycemic effect. The most-common name is soursop, referring to its sour and sweet flavors, while in Malaysia, this tree is commonly called ‘durian belanda’. Furthermore, A. muricata contains a high content of phenolic compounds in the roots and leaves. In vitro and in vivo studies have shown that A. muricata has the pharmacological effects of anti-cancer, anti-microbial, antioxidant, anti-ulcer, anti-diabetic, anti-hypertensive, and wound healing. With regard to its anti-diabetic effect, mechanisms of inhibiting glucose absorption via α-glucosidase and α-amylase activity inhibition, increasing glucose tolerance and glucose uptake by peripheral tissues, and stimulating insulin release or acting like insulin were deeply discussed. There is still a significant research gap, and future studies are required to conduct detailed investigations and gain a better molecular understanding of A. muricata’s anti-diabetic potential, especially by using the metabolomics approach.


Introduction
Plants have had various significant benefits for thousands of years worldwide, discovered based on traditional knowledge. Even now, plants continue to contribute to new remedies for human beings [1]. Annona muricata Linn. (Annonaceae) has been utilized as a medicinal remedy for many years, attracting many scientists to investigate this plant. A. muricata L. is a lowland tropical fruit-bearing tree of the Annonaceae family. Graviola, soursop, durian belanda, and guanabana are the popular Malaysian local names for A. muricata. Annona's genus name might be derived from the Latin word 'anon,' which means 'yearly produce'. It could be elaborated as "the fruit production habits of the numerous A. muricata is a small evergreen tree ( Figure 2). It can be slender and upright or low spreading and bushy and becomes straggly as it matures. It is 5 to 10 m tall, 15 to 83 cm in diameter, and has low branches. When the dark-green leaves are crushed, they emit a strong odor [20]. The hermaphrodite flowers, which have a unique fragrance, are generally produced singularly or in small clusters on ancient wood. The flowering phase begins at age 3 to 4, though this may vary depending on the environment. The fruit is heartshaped to oval, depending on its pollination. The fruiting occurs most of the year, but it may become seasonal, depending on the altitude. The fruit will become distorted with an irregular shape and undersized when it has poor pollination and unfertilized ovules fail to develop. The skin has many recurved soft spines 0.5 to 1.3 cm apart [19]. The fruit's flesh comprises an edible white pulp, fiber, and a core of indigestible black seeds. The pulp is also used for flavor sweets, sorbets, and ice cream, as well as fruit nectar, A. muricata is a small evergreen tree ( Figure 2). It can be slender and upright or low spreading and bushy and becomes straggly as it matures. It is 5 to 10 m tall, 15 to 83 cm in diameter, and has low branches. When the dark-green leaves are crushed, they emit a strong odor [20]. The hermaphrodite flowers, which have a unique fragrance, are generally produced singularly or in small clusters on ancient wood. The flowering phase begins at age 3 to 4, though this may vary depending on the environment. The fruit is heart-shaped to oval, depending on its pollination. The fruiting occurs most of the year, but it may become seasonal, depending on the altitude. The fruit will become distorted with an irregular shape and undersized when it has poor pollination and unfertilized ovules fail to develop. The skin has many recurved soft spines 0.5 to 1.3 cm apart [19]. The fruit's flesh comprises an edible white pulp, fiber, and a core of indigestible black seeds. The pulp is also used for flavor sweets, sorbets, and ice cream, as well as fruit nectar, smoothies, and fruit-juice beverages. Unless a blender is used for processing, the seeds are usually left in the recipe and removed when eating. smoothies, and fruit-juice beverages. Unless a blender is used for processing, the seeds are usually left in the recipe and removed when eating.

Ethnomedicinal Uses
All parts of A. muricata have been used for centuries to cure many ailments and wounds. The method of preparation varies from topical applications, direct ingestion, decoctions, and juicing. Based on a review on the pharmacological activities of A. muricata, it has long been used to treat a variety of conditions, including cancer, diabetes, hypertension, respiratory illnesses, fever, and bacterial infections ( Figure 3) [21,22]. This plant is widely used traditionally to treat various diseases in South and North America, as well as West Africa [23]. The bark, root, seed, and leaf of A. muricata are widely decocted for

Ethnomedicinal Uses
All parts of A. muricata have been used for centuries to cure many ailments and wounds. The method of preparation varies from topical applications, direct ingestion, decoctions, and juicing. Based on a review on the pharmacological activities of A. muricata, it has long been used to treat a variety of conditions, including cancer, diabetes, hypertension, respiratory illnesses, fever, and bacterial infections ( Figure 3) [21,22]. This plant is widely used traditionally to treat various diseases in South and North America, as well as West Africa [23]. The bark, root, seed, and leaf of A. muricata are widely decocted for medical and treatment purposes. In Indonesia and South Pacific countries, soursop leaves are used in a bath to cure skin ailments. Discomfort, such as asthma, colds, and flu, are also managed using the leaves, especially in Mexico and Brazil. Other countries, such as Martinique and Nicaragua, also use it with the same purpose, as stated in a review [24]. Moreover, these Life 2023, 13, 353 5 of 29 leaves are applied topically by people in New Guinea and Ecuador to reduce pain. In Malaysia, the leaves are used to treat external and internal parasite infections and malaria. The leaves are used to treat insomnia, diabetes, headaches, and cystitis [21,22]. In Tanzania, which is in Eastern Africa, the leaves of A. muricata are among the most-used plants to cure diabetes. This medication is available locally and is purchased by patients via marketplaces, neighbours, or traditional medicine sellers, and some participants reported that they had cultivated therapeutic plants near their houses. According to local herbalists, they obtained the ingredients they used to treat diabetes locally and created them themselves based on their experience. Its decoction is consumed in minimal doses to lower blood-glucose levels. The interview emphasized that there is a certain quantity that patients must follow since it is highly powerful and may bring adverse effects or an excessive reduction in glucose level. Furthermore, if the medication is in liquid form, most of the patients combine it with warm water, milk, tea, cereal, or drink it directly [21]. At the same time, its decoction is administered topically for anti-rheumatic and neuralgic effects, as well as to reduce abscesses [25].

Medicinal Uses
A. muricata L. is a coveted tropical tree that has been widely used in folk medicine worldwide. Some of these uses are supported by scientific evidence, mostly through in vitro and in vivo studies. Medicinal plants are also protected by stringent intellectual property laws to support their traditional uses in treating various disease conditions. Despite the theoretical differences between traditional and modern medicine, both approaches are complementary. Moreover, A. muricata leaves are now utilized to control and treat diabetes, cancer, and hypertension [8]. Acetogenins are the most-abundant phyto- Other than leaves, the fruit is also utilized for medicinal uses. In addition to being tasty, the juice is used to treat heart disease, liver disease, and diarrhoea by acting as a galactagogue. The juice is taken as a beverage in South America to eliminate intestinal parasites. On the other hand, the powder from the toasted seed of A. muricata is used as an Life 2023, 13, 353 6 of 29 emetic agent and laxative. Moreover, when mixed with grease to make lotion, the powder can treat parasitic skin disorders [26]. In addition, barks of A. muricata are being used to treat hypertension, diabetes, inflammation, parasite infection, and as a smooth-muscle relaxant [2]. In several tropical Sub-Saharan African countries, including Uganda, all parts of A. muricata are used to treat malaria, stomachache, parasite infections, diabetes, and cancer. The roots, leaves, seeds, and unripe fruit are also used as bioinsecticides, biopesticides, and insect repellents on the skin. In India, A. muricata's roots, bark, and leaves are reported to have antiphlogistic and anthelmintic effects, while the plant's flowers and fruits are used to treat catarrh. Furthermore, A. muricata aqueous extract is utilized to manage insects, such as lepidopteran larvae, aphids, and thrips [19]. A. muricata has been used in combination with other plant species. In Malaysia, a mixture of leaves from A. muricata, Hibiscus rosa-sinensis L., and A. squamosa is made into juice and applied on the head to prevent fainting [19]. In summary, every part of the A. muricata tree has its own beneficial effects. Older people also continuously apply this plant in treating certain diseases, showing its effectiveness as a remedy.

Medicinal Uses
A. muricata L. is a coveted tropical tree that has been widely used in folk medicine worldwide. Some of these uses are supported by scientific evidence, mostly through in vitro and in vivo studies. Medicinal plants are also protected by stringent intellectual property laws to support their traditional uses in treating various disease conditions. Despite the theoretical differences between traditional and modern medicine, both approaches are complementary. Moreover, A. muricata leaves are now utilized to control and treat diabetes, cancer, and hypertension [8]. Acetogenins are the most-abundant phytoconstituents in A. muricata and are characteristic of Annonaceae. Other phytochemicals reported in this species are alkaloids and phenolics. Leaves are among the most-researched plant organs, most likely because they are the most commonly utilized as medicine, while the fruits are an exotic commodity. There is mounting evidence that A. muricata has anti-cancer properties. This is because of its acetogenin content that has cytotoxic properties, causing apoptosis in cancer cells [2]. Acetogenins are a unique group of derivatives of long-chain fatty acids generated from the polyketide pathway. More than 120 acetogenins have been recorded from the leaves, stems, bark, seeds, pulp, and fruit peel of A. muricata in earlier phytochemical studies, and around 46 acetogenins have been discovered from the leaves [19].
This plant is commonly used to treat diabetes traditionally and research demonstrated that the leaves and fruit pulp are the most efficient as alternative diabetes treatment. This is partly because this plant has the ability to inhibit α-glucosidase and α-amylase activity, thereby preventing an increase in blood-glucose levels [9]. On the other hand, A. muricata leaves are believed to control convulsive seizure and fever, which has been investigated by Gouemo and colleagues. Another study showed that treatment with an ethanolic extract from the leaves reduced the incidence and mortality rate of seizures [2]. Furthermore, leaves, barks, roots, and seeds of A. muricata demonstrated high anti-bacterial action against Staphylococcus aureus, Pseudomonas, Bacillus, Klebsiella, and E. coli, as suggested by earlier investigations [27]. This anti-bacterial effect may partially clarify the use of leaf extracts to treat urinary tract infections, diarrhea, pneumonia, and skin disease. A. muricata has also been used as a biopesticide, especially in controlling mosquito breeding. A study suggested this happened as the plant's acetogenins can cause toxicity to the mosquito larvae [24]. Furthermore, A. muricata may have the potential to boost one's immune system through the activation of mitogen-activated protein (MAP) kinase signaling pathways [28]. Its phenolic components, which include tannins, flavonoids, phenolic acids, and lignin, can increase the body's antioxidant potential. This condition reduces inflammation and prevents bleeding and hemorrhoids. Moreover, the ability of A. muricata to inhibit αglucosidase activity better than α-amylase activity, resulting in an anti-diabetic effect, is attributed to its phenolic-rich content [5]. Lastly, based on a review paper, flavonoids and alkaloids in A. muricata can decrease blood cholesterols in an animal model, which can lead to a hypotensive effect [29].

Phytochemistry and the Pharmacological Effect of A. muricata
Extensive phytochemical analyses on various parts of the A. muricata plant have revealed the presence of a variety of phytoconstituents and bioactive compounds. Thus, 212 compounds have been identified in this plant, with acetogenins being the most prevalent [8]. Other compounds that can be identified are alkaloids and phenolics, all of which are listed in Table 1 along with their effects. These compounds were analyzed through High-Performance Liquid Chromatography (HPLC), Nuclear Magnetic Resonance spectroscopy (NMR), Fourier-Transform Infrared spectroscopy (FTIR), Kedde's reagent, and HPLC coupled with a photodiode array detector (HPLC-DAD) [30][31][32].
Much research has been carried out on A. muricata to evaluate its pharmacological effect, in which a systematic review was conducted to incorporate the scientific studies published up to February 2017, deducing that only 2% had been conducted as clinical trials, 2% in silico modelling, 36% for in vivo studies, and most studies regarding this plant were carried out through in vitro studies [24]. The extract used was mainly based on organic solvents, as opposed to traditional preparations using water. The advantage of solvent extraction is due to the effectiveness in extracting most bioactive compounds [24]. The pharmacological effect of A. muricata is simplified in Figure 4, including in vivo and in vitro studies.

Cytotoxic Activity
Many investigations have been carried out to study the anti-cancer properties of A. muricata. The cytotoxic activity of this plant occurs due to the presence of acetogenin, which is the most-abundant chemical family in various parts of A. muricata. The proposed mechanism of action for the selected acetogenins is explained in Figure 5. Acetogenins and flavonoids contained within the leaves can hinder human prostate cancer cell line PC-3 proliferation. This effect occurs as they promote necrosis by inhibiting cellular metabolism and tumor mobility [22]. Annonacin compounds showed the ability to mediate apoptotic cell death by increasing DNA fragmentation and cleavage of caspase-3. This process stops the proliferation of endometrial cancer cell lines, including HEC-1A and ECC-1. The cellular damage can also be prevented using ethanol extract leaves by up-regulating the expression of superoxide dismutase-1 of antioxidant enzyme expression [24]. This expression leads to a breakdown of superoxide, allowing the cell to function. Other than that, annomuricin E is capable of inhibiting HT-29 cell growth. Annomuricin causes cytochrome c to leak from the mitochondria by disturbing the matrix metalloproteinases (MMPs). Thus, pro-apoptotic factors, such as caspase-3, caspase-7, and caspase-9, will be activated [22].
On the other hand, the application of A. muricata extracts on fibrosarcoma cells (HT1080) can suppress the MMP-2 and MMP-9, hindering cancer progression. The proliferation of human leukemia cell line HL-60 can be suppressed using extracts from A. muricata leaves, roots, and twigs [22]. This effect is due to the reduction in reactive oxygen species (ROS) generation, a halt in G0/G1 cell cycle, and a disruption in MMPs. Meanwhile, the administration of ethyl acetate extract and ethanol extract can increase caspase-3 and caspase-9 expression while decreasing Bcl-2 expression. This process activates MCF7 cell apoptosis. Ethyl acetate extract from leaves alone can enhance the expression of caspase-3 in colorectal cancer cell line COLO-205 and breast cancer lines. A. muricata extract also has selective action on breast cancer by inducing apoptosis to up-regulate the Bax, down-regulate the expression of Bcl-2, and inhibit the cell cycle at the G0/G1 phase [19].    3. Cis-annomuricin-D-one, trans-annomuricin-D-one [37] Leaves Cytotoxic [37] Toxicity against lung cancer cells A549 with ED 50 of <10 −2 µg/mL, colon HT-29 with ED 50 of <10 −2 µg/mL, and pancreatic PACA-2 with ED 50 of <10 −2 µg/mL [37].

Annonacin A [42]
Leaves, seeds, pericarp Cytotoxic [42] Could possibly reverse MDR, which is caused by ABCB1 in colorectal cancer. This would make it possible for the tested anti-cancer drugs to work better against tumours [42].

Anti-Protozoal Activity
A. Muricata also exhibits therapeutic potential against protozoans that caused amebiasis diseases, chagas, schistosomiasis, malaria, and leishmaniasis [8]. The most-effective part of A. muricata in anti-protozoal activity is the seed, as it contains annonacinone, acetogenins, and corossolone [22]. A study showed that the extract from leaves of A. muricata can inhibit the growth of Plasmodium but is less effective against Toxoplasma. This concluded that A. muricata has an anti-protozoal effect and the degree of effectiveness varies [80].

Antioxidant Activity
Many diseases (i.e., cardiovascular diseases, arthritis, and cancer) arise due to reactive oxygen species (ROS). Studies showed that A. muricata contains vitamins, carotenoids, flavonoids, and phenolic acids, all of which have antioxidant properties ( Table 1). The flavonoids, such as gallocatechin, kaempferol, quercetin, rutin, and argentinine, that are abundant in the leaf part may contribute to its potent antioxidant effect and improve other conditions caused by high ROS levels by donating hydrogen [22]. Another study also stated that the ethanolic extract of A. muricata is more effective compared to the aqueous extract of the plant since ethanolic extract sustains more secondary metabolites compared to aqueous extract [81]. The content of antioxidant compounds depends on the solvents used for the extraction, in which more compounds can be extracted in polar solvents compared to non-polar solvents [81].

Anti-Viral Activity
Regarding anti-viral bioactivity, A. muricata extracts exhibit virucidal activity by interfering with HIV-I replication early in the infection. The plant extracts reduce the risk of viral particle transmission by lowering viral RNA input and interfering with the function of envelope proteins during virus entry into the host cell [8]. In addition, it also prevents the virus from attaching to the host cell. The stem and bark of A. muricata ethanolic extract showed in vitro anti-viral effects against the herpes simplex virus, in which the minimum inhibitory concentration was 1 mg/mL. Moreover, the acidified ethanolic extract reduced viral multiplication after 1 h of contact. This plant's anti-viral properties are due to phenolics [22]. It is reported that rutin is the most-abundant component that inhibits viral replication. Furthermore, flavonoid glycosides, quercetin, and naringenin inhibit the spread

Anti-Cancer Activity
A randomized control trial on colorectal patients administrated with 300 mg of A. muricata extract containing 0.36% acetogenins after breakfast showed suppression in colorectal cancer cell growth [83]. Acetogenins hamper the ATP formation process required by cancer cells to grow in the complex 1 mitochondrial electron transport chain, as shown in Figure 6. In addition, G1 cell cycle arrest causes mitochondria-mediated apoptosis [22]. Acetogenins induce apoptosis by increasing ROS formation, ann pro-apoptotic Bax protein, and down-regulating antiapoptotic Bcl-2 protein. These processes impair the mitochondrial membrane potential and then cause the release of cytochrome c. This cytochrome c activates apoptosomes and the intrinsic caspase cascade initiates DNA fragmentation, resulting in apoptosis execution ( Figure 6). Annocherimolin, an acetogenin, has cytotoxic activity against HT-29 colon cancer cells [24]. adenosine triphosphate (ADP), which is used by this molecule to activate the pump for cancer drug removal. Hence, acetogenins have been suggested to make chemotherapy more effective. Some studies also proposed that acetogenins have chemotherapeutic potential, especially in cancer cells that have developed resistance to medications [24].

Anti-Ulcer
Gastric ulcers are caused by excessive amounts of gastric acid secreted in the stomach and a decrease in gastric-wall mucus. Moreover, ROS also contributes to this damage. A. muricata plants possess gastroprotective properties, most probably due to antioxidant compounds. These compounds can increase the mucosal nonprotein sulfhydryl group content and improve gastric lesions. A. muricata extract can reduce stomach acidity and significantly reverse the loss of gastric-wall mucosa, similar to the effects of proton pump inhibitors, such as omeprazole. The A. muricata extract improves the amount of several enzymes that can lower cellular ROS, including nitric oxide (NO), glutathione (GHS), catalase (CAT), prostaglandin E2 (PGE-2), superoxide dismutase (SOD), as well as malondialdehyde (MDA) [8].
According to a survey, A. muricata leaves and bark are frequently brewed as tea to cure digestive issues, such as gastritis and poor digestion. Other preparations of A. muricata using ethyl acetate showed anti-ulcer activity by protecting stomach-wall damage and scavenging ROS in rats with ethanol-induced gastric injury. The inhibition of gastric damage is accomplished by up-regulating Hsp70 and down-regulating Bax, which are crucial mechanisms in anti-ulcer action [22].

Anti-Inflammatory Activity
Several studies have shown that A. muricata has anti-inflammatory effects, with the leaf being the most commonly studied. A. muricata leaf extract inhibits inflammatory mediators, such as nitric oxide (NO), TNF-α, IL-6, and IL-1β; hence, they have the potential On the other hand, the acetogenin compound in A. muricata is capable of inhibiting NADH oxidase, which will affect the production of ATP later on. ATP is crucial for cancer cells as it helps them to proliferate [22]. In addition, it also blocks the production of adenosine triphosphate (ADP), which is used by this molecule to activate the pump for cancer drug removal. Hence, acetogenins have been suggested to make chemotherapy more effective. Some studies also proposed that acetogenins have chemotherapeutic potential, especially in cancer cells that have developed resistance to medications [24].

Anti-Ulcer
Gastric ulcers are caused by excessive amounts of gastric acid secreted in the stomach and a decrease in gastric-wall mucus. Moreover, ROS also contributes to this damage. A. muricata plants possess gastroprotective properties, most probably due to antioxidant compounds. These compounds can increase the mucosal nonprotein sulfhydryl group content and improve gastric lesions. A. muricata extract can reduce stomach acidity and significantly reverse the loss of gastric-wall mucosa, similar to the effects of proton pump inhibitors, such as omeprazole. The A. muricata extract improves the amount of several enzymes that can lower cellular ROS, including nitric oxide (NO), glutathione (GHS), catalase (CAT), prostaglandin E2 (PGE-2), superoxide dismutase (SOD), as well as malondialdehyde (MDA) [8]. According to a survey, A. muricata leaves and bark are frequently brewed as tea to cure digestive issues, such as gastritis and poor digestion. Other preparations of A. muricata using ethyl acetate showed anti-ulcer activity by protecting stomach-wall damage and scavenging ROS in rats with ethanol-induced gastric injury. The inhibition of gastric damage is accomplished by up-regulating Hsp70 and down-regulating Bax, which are crucial mechanisms in anti-ulcer action [22].

Anti-Inflammatory Activity
Several studies have shown that A. muricata has anti-inflammatory effects, with the leaf being the most commonly studied. A. muricata leaf extract inhibits inflammatory mediators, such as nitric oxide (NO), TNF-α, IL-6, and IL-1β; hence, they have the potential to treat inflammation [19]. Oral administration of A. muricata ethanolic leaf extracts (10, 30, 100, and 300 mg/kg) significantly reduced carrageenan-induced paw edema, demonstrating the plant's anti-inflammatory properties. Leukocyte migration and exudate volume were reduced along with this anti-inflammatory action. The same extract, administered orally to mice, significantly reduced abdominal contortions generated by acetic acid (0.6% v/v), displaying a potent anti-nociceptive effect [2].

Hypotensive Activity
According to research results, A. muricata exhibits hypotensive action, which can reduce blood pressure by blocking calcium ion channels rather than engaging endotheliumand nitric-oxide-dependent mechanisms. Ca+ antagonism during this mechanism tones down the high activity of K+ that can induce contractions [2]. Another study stated that this mechanism did not affect the heart rate but did affect the blood pressure. Administration of A. muricata leaf extract to normotensive rats showed significantly declined dose-dependent blood pressure. In addition, the combination of A. muricata with Persea americana showed a positive result for anti-hypertensive activity [22]. A. muricata's hypotensive effect could be attributed to the alkaloid compounds found in the plant's leaves. Isoquinoline, coreximine, and anomurine, alkaloids, have been shown to have a transient depressive effect on blood pressure [84].

Wound Healing
This plant showed a compromising wound-healing activity, especially from the leaf and bark extract [2]. A wound heals in four stages: coagulation, inflammation, proliferation, and maturation [8]. Several of these phases are accelerated by the administration of A. muricata extract. Heat-shock proteins (Hsp70) expressed during the inflammatory phase are crucial for healing due to their role in cell proliferation, and A. muricata caused a significant increase in Hsp70 [2]. A large amount of the cytokines and free radicals produced during this phase by the inflammatory cells might cause lipid peroxidation in the wound. Tissues treated with A. muricata extract showed enhanced glutathione peroxidase (GPx), SOD, and CAT activity, which protects tissue from oxidative damage and speeds up the healing process. Furthermore, ethyl acetate leaf extract of A. muricata reduces MDA, a lipid peroxidation biomarker that can damage collagen, fibroblast, and endothelial cell metabolism, which are critical for wound healing [85]. This was supported by a study on ethyl acetate extract at a low dose of 5%w/w and a high dose of 10%w/w against a wound created on the neck. During the maturation phase, collagen accumulated and fibroblasts multiplied. According to a histological study, A. muricata extracts increased the number of collagen fibers deposited in the wound [85].

Anti-Diabetic Effect of A. muricata
DM is a chronic metabolic disorder characterized by high blood-glucose concentrations caused by insulin deficiency, frequently accompanied by insulin resistance. DM is also a leading cause of disability and hospitalization, resulting in a significant financial burden. Many traditional plant treatments for DM are used worldwide. Diabetes management with no side effects remains a challenge for the medical system. As a result, there is a growing demand for natural products with anti-diabetic activity with few side effects [86]. A. muricata is known to be traditionally applied in treating diabetes mellitus. Research showed that it has potential bioactive compounds to reduce high blood-glucose levels. Hence, this review emphasizes the anti-diabetic effect of A. muricata as well as its pharmacological properties in the hypoglycemic effect. This review aims to aid in strengthening the understanding between traditional medicine, pharmacology, and mechanism of action of A. muricata in terms of an anti-diabetic effect.

Hypoglycemic Activity of A. muricata
Flavonoids in A. muricata have anti-diabetic properties. This effect is due to its ability to inhibit the activity of α-glucosidase, as this enzyme is responsible for catalyzing the breakdown of starch into simple sugars. These enzymes help humans digest carbs and starches in their diets to create glucose for intestinal absorption, which raises blood-sugar levels. Hence, this process is inhibited with the presence of flavonoids and prevents the intestine from absorbing the carbohydrate [22]. Moreover, the modulation of glucose absorption, insulin signaling, insulin secretion, and adipose deposition is also supported by flavonoids. They focus on different molecules that are involved in the regulation of several pathways, such as enhancing β-cell proliferation, enhancing insulin secretion, lowering apoptosis, and enhancing hyperglycemia through controlling liver glucose metabolism [87,88]. Some studies linked triterpenoids, tannins, and flavonoids with anti-diabetic activities. These properties may act through various pathways, including promoting insulin production, boosting β-cell repair or proliferation, and amplifying the effects of insulin and adrenalin [86].
Aqueous extract of A. muricata exhibits anti-diabetic benefits through antioxidant processes. A. muricata leaf extract reduced lipid peroxidation processes in streptozotocininduced diabetic mice and indirectly impacted the synthesis of insulin and endogenous antioxidants [8]. Moreover, studies revealed that diabetic albino Wistar rats had a bloodglucose level reduction after treatment with A. muricata extract. Moreover, the pancreatic β cells in diabetic albino Wistar rats also did not exhibit the changes often observed when they were treated with A. muricata leaves. Furthermore, the blood-glucose levels, body weight, food and water consumption, lipid profile, and oxidative defenses all returned to normal [15].
A. muricata fruit extracts have been shown to have antioxidant and anti-diabetic properties in vitro by inhibiting essential type 2 diabetes-related enzymes, such as αamylase and α-glucosidase. According to a study, its pericarp possesses the highest antioxidant-and enzyme-inhibitory capabilities. Additionally, A. muricata seed oil has shown promising anti-diabetic properties against streptozotocin-induced type 1 diabetes. A study revealed that compared to the control group, an experimental mouse treated with A. muricata seed oil had considerably lower blood-glucose levels and the pancreatic-isletpreserved area was also improved [22]. In addition to having anti-diabetic properties, according to a review, the extract dramatically decreased serum levels of total cholesterol, low-density lipoprotein, triglycerides, and very-low-density lipoprotein cholesterol [8].

In Vivo and In Vitro Study on Anti-Diabetic Effect
Son et al., 2021, as stated in Table 2, investigated the anti-hyperglycemia-induced liver damage from A. muricata extracts in type 2 diabetic mice. After chronically inducing diabetes in C57BL/6J male mice with STZ, two groups of mice were given ethanolic leaves of A. muricata extract at 50 mg/kg and 100 mg/kg doses, respectively. Normal and diabetic controls were designated as NC and DMC, respectively, whereas low and high doses of the Life 2023, 13, 353 18 of 29 extract were designated as LAM and HAM, respectively. This study discovered substantial differences in liver weight between rats fed with extract, NC, and DMC [89]. There were no differences in body weight or food consumption between extract-treated and DMC rats ( Table 2).
A. muricata extract regulated glucose homeostasis by lowering blood-glucose levels. At modest dosages (50 mg/kg of the extract), the fasting blood glucose (FBG) and plasma insulin levels in diabetic rats were significantly decreased. There was a significant difference in haemoglobin A1c (HbA1c) levels and oral glucose tolerance test area-under-the-curve measurement between the LAM and HAM rats and the DMC group. These data supported prior research on the A. muricata extract, which reduced blood-glucose levels. A recent study showed that rutin can lower blood glucose and plasma insulin levels, whereas quercetin and kaempferol have hypoglycemic effects through modulating energy balance. The insulin signalling parameter revealed that modest supplementation of ethanolic leaves of A. muricata extract improved the insulin signalling pathway via a substantial increase in IRS-1 and GLUT2 proteins compared to the DMC group. As a result, even at modest doses, the injection of an extract comprising rutin, quercetin, kaempferol, and acetogenins appears to be beneficial in controlling diabetes metabolic abnormalities by increasing the insulin signalling pathway [89].
The hepatic morphology and hepatic triglyceride (TG) characteristics of the DMC group had significantly higher fat accumulation than rats in the NC group. Compared to the DMC group, the extract treatment reduced the number and size of lipid droplets. Hepatic TG was abnormally greater in the DMC group compared to the NC group but returned to near normal in the LAM group. All of the effects of the extract on cholesterol demonstrated its capacity to reduce hepatic triglycerides and plasma LDL cholesterol levels, lowering fat buildup in the liver and avoiding NAFLD. AST indicated no changes in hepatic damage. The DMC group, on the other hand, had much greater ALT levels than the NC group. Compared to DMC, rats in the LAM group had significantly lower ALT levels, unlike the HAM group. As a result, treatment of the extract prevents liver injury by reducing fat formation, suggesting that its protective impact was not dose-dependent. A. muricata extract is expected to reduce the incidence of diabetic liver disease in the long run while having fewer negative effects on the body [89].
An imbalance of free radicals and antioxidants causes oxidative stress, which harms cells and tissues. The DMC group had considerably higher amounts of oxidation products, 4-HNE, and protein carbonyls than the NC group. Extract therapy, on the other hand, decreased hyperglycemia-induced hepatic oxidative stress. The level of 4-HNE in the HAM group was substantially lower than in the DMC group. Only the amounts of protein carbonyls in the LAM group were considerably lower than in the DMC group. Other oxidative stress variables, including Nrf2 and NQO1 levels, showed significant variations between the DMC and the LAM, showing that extract therapy can ameliorate diabetic tissue damage by reducing oxidative stress [89].
In the energy metabolism indicator parameter, the DMC group had a substantially lower AMPK-mTOR pathway than the NC group. Increased levels of p-AMPK and PGC1 in LAM-treated rats restored energy metabolism. Furthermore, compared to DMC, p-mTOR was considerably lower in the treatment groups. It appears that low doses of extract contribute to the normalisation of energy metabolism by increasing AMPK/PGC1 levels, which are decreased in T2DM. To summarize, a small amount of extracts contain enough quercetin and kaempferol to regulate energy balance and provide a hypoglycemic effect [89]. Table 2. Anti-diabetic effect of A. muricata L. and its bioactive compounds in the involved biochemical parameters determined through in vivo and in vitro studies. • LAM-treated rats have normalized energy metabolism through increased levels of p-AMPK and PGC1α.

Part of A. muricata
• p-mTOR was significantly decreased in the treatment groups compared to DMC.  The autophagy process was suppressed by a reduction in p-AMPK and an elevation in p-mTOR, resulting in reduced LC3-II expression in DMC compared to NC. In contrast, LC3-II expression was considerably higher in extract-treated groups compared to DMC. For lipid metabolism, the proteins associated with fat production in the LAM group were considerably decreased to normal levels compared to DMC in the extract-treated group. As a control, proteins involved in fat synthesis were considerably increased in the DMC group compared to the NC group. Autophagy was restored after a low-extract supplementation by increasing AMPK and decreasing p-mTOR levels. The findings imply that in diabetic conditions, the extract supplementation might regulate hepatic lipid homeostasis, lipophagy activation, and the AMPK-mTOR pathway [89].
In summary, a low dose of extract treatment was more effective in regulating insulin signalling, energy metabolism, and lipid metabolism compared to a high dose of extract. This observation considers that molecular pathways can be selectively regulated at different doses of extract as they contain different amounts of bioactive compounds. Low-dose extract at 50 mg/kg was the most-effective dose and might be tissue-specific in diabetes, with fewer side effects on the body system.
Setiadi et al., 2019, evaluated the anti-hyperglycemic efficacy of an ethanolic extract of soursop leaf (A. muricata L.) and acarbose in diabetic rats induced by streptozotocin (STZ). This experimental study involved pre-and post-tests on five groups of rats, two control groups and three treatment groups. The rats are divided into two control groups, (C(-) received water and C(+) received acarbose) and three treatment groups (T1 received 10 mg/BW extract, T2 received 20 mg/BW extract, and T3 received 30 mg/BW extract). The treatment lasted for 1 week, and blood-glucose levels were measured before and after treatment. Blood-glucose levels in the pre-test experimental groups remained the same. Following treatment, all treatment groups showed significant (p < 0.05) changes in blood-glucose levels (reduction) after being treated with different doses of leaf extract. Comparing pre-and post-treatment for each group, the paired T-test revealed significant differences for the positive control group and treatment groups. Treatment group 3 (T3, 30 mg/kg soursop leaf extract) had the greatest anti-hyperglycemic impact, and it reduced blood glucose similar to the acarbose group (positive control) ( Table 2) [90].
A. muricata leaves are reported to contain components, such as flavonoids, tannins, and alkaloids, that can heal pancreatic tissue in diabetic patients. A. muricata leaves contain flavonoid derivatives, such as quercetin. Flavonoids reduce blood-sugar levels in various ways, including blocking glucose absorption, improving glucose tolerance and uptake by peripheral tissues, boosting insulin production or functioning as insulin, and modulating enzymes involved in carbohydrate metabolism. The flavonoids quercetin and chrysin can serve as hypoglycemic agents at high doses. This prevents an increase in blood-glucose levels by encouraging cells to make more insulin. In vitro studies further reveal that quercetin can impede glucose transport through the intestinal glucose transporters 2 (GLUT2) and 5 (GLUT5), which are responsible for glucose absorption in the small intestine [90].
Tannins are known to promote glucose and fat metabolism. They lower blood-sugar levels by boosting glycogenesis. This chemical can also function as an astringent or chelating agent, shrinking the small-intestine epithelial barrier and limiting food absorption. As a result, the rate of blood-glucose levels will be reduced. Tannins can also lower blood-glucose levels by boosting glucose absorption via phosphoinositide 3-kinase and mitogen-activated protein kinase activation (MAPK). Gallotanins and ellagitanins are two types of hydrolyzed tannins reported in A. muricata. Gallotanins can improve glucose absorption while preventing adipogenesis. Ellagitanins (insulin-like substance) exhibit characteristics comparable to insulin and can improve glucose transport activity into fat cells in vitro. Furthermore, tannins contain antioxidant properties and have been demonstrated to suppress tumor development [90].
Alkaloids lower blood-glucose levels by blocking glucose absorption in the gut and gluconeogenesis enzymes. They inhibit the enzymes glucose 6-phosphatase and fructose 1,6-bisphosphatase, which decrease the generation of glucose from non-carbohydrate substrates. Alkaloids also boost glucose oxidation via glucose 6-phosphate dehydrogenase, resulting in lower blood-glucose levels [90].
Using alloxan-induced diabetic rats, Sovia et al. (2017) discovered the hypoglycemic and hypolipidemic effects of A. Muricata leaf extract. This experimental study involved pre-and post-tests on five groups of rats, two control groups and three treatment groups. Control group Group 1 (G1) was given water and Group 2 (G2) was given alloxan. For the treatment groups, Group 3 (G3) was given 50 mg/extract, Group 4 (G4) was given 100 mg/extract, and Group 5 (G5) was given 200 mg/extract. The treatment was 21 days, and blood-glucose levels were measured before and after treatment. The results revealed that A. muricata treatment caused a considerable drop in blood-glucose and cholesterol levels. No changes were detected in the histological structure of the islet of Langerhans [91].
The hypoglycemic impact of flavonoids found in A. muricata leaf extract was achieved through boosting insulin production, inhibiting beta-cell death, and regulating proliferation. Flavonoids have also been shown to enhance Ca2+ absorption from isolated islet cells, which drive beta cells to make insulin. As a result, this activity may assist non-insulindependent diabetics with no insulin production. The flavonoid also plays a key part in A. muricata's hypolipidemic action since it protects low-density lipoprotein (LDL) from oxidative changes. This hypolipidemic impact is frequently linked to its anti-diabetic and antioxidant properties. A. muricata's anti-diabetic impact lowers the conversion of excess glucose to LDL, while its antioxidant function protects LDL from oxidative damage, lowering the risk of cardiovascular-diabetic problems. A previous study with STZ-induced diabetes showed that A. muricata extract may protect and preserve pancreatic cell integrity from oxidative stress, resulting in a considerable improvement in the islet of Langerhans. In alloxan-induced diabetic rats, however, extract treatment did not restore the islet of Langerhans. It might be because the extract dose employed in this study was insufficient to enhance the islet of Langerhans [91]. Adefegha et al. (2015) investigated the effects of aqueous extracts (1:100 w/v) of A. muricata fruit parts (pericarp, pulp, and seed) on α-amylase, α-glucosidase, and angiotensin-I converting enzyme (ACE) inhibition in vitro, as stated in Table 2. This study also examined the extracts' radical scavenging and Fe 2+ chelation activities, as well as their reducing and phenolic contents [5]. The extracts inhibited α-amylase, α-glucosidase, and ACE activities in a dose-dependent manner. Pericarp extract demonstrated the highest inhibitory effect in α-amylase, α-glucosidase, and ACE from the result of 50% antioxidant activity (EC 50 ). In contrast, the seed extract demonstrated the lowest inhibitory activity across all experiments. In all experiments, the inhibitory actions of pericarp extract were lower than those of the positive controls acarbose and captopril [5]. Phenolic distributions in A. muricata extracts contributed to their enzyme inhibitory and antioxidant properties. The scavenging of radicals from all extracts confirmed that the pericarp extract had the greatest total phenol and flavonoid content, followed by the pulp and seed, which had the lowest. The inhibition of α-glucosidase was greater than that of α-amylase, which was consistent with a prior study that found plant phenolic-rich extract reduced α-glucosidase activity better than α-amylase activity. Anti-hypertensive ACE inhibitors have been shown to lessen the chance of acquiring type 2 diabetes. The release of bradykinin in response to ACE inhibitor activation may improve the responsiveness of muscle fibres and adipocytes to insulin usage [5]. The ability of the A. muricata fruit portions (pericarp, pulp, and seed) to decrease oxidative-stress-induced metabolic illnesses, such as diabetes and hypertension, was highly effective. The mechanism of action of A. muricata is simplified in Figure 7.

Conclusions and Future Perspective
In conclusion, A. muricata is widely used in traditional medicine to treat a variety of ailments, such as hypertension, diabetes, and cancer. Research also stated that these plants contain various types of bioactive compounds from certain classes, such as acetogenins, flavonoids, phenols, alkaloids, and megastigmane. In vivo and in vitro research showed that it has potential to treat various conditions, such as wound healing, ulcer, inflammation, cancer, diabetes, and hypertension. In this review, we summarized the traditional uses, medicinal uses, chemical constituents, and pharmacological effects of A. muricata. In addition, we also emphasized the effect of A. muricata towards an anti-diabetic effect. There is still a significant research gap, and future studies are required to conduct detailed investigations and better understand A. muricata's anti-diabetic potential. In addition, the biological studies conducted by using this crude extract are still limited to anti-diabetic effects. Meanwhile, there is no thorough metabolomic study carried out for this potential effect. The metabolite changes that are revealed from the effect of bioactivities have not been identified. Hence, the mechanisms of action cannot be well determined. Finally, A. muricata has a bulk of evidence on the anti-diabetic effect and the potential as an alternative diabetes mellitus treatment. However, major steps to conduct more metabolomic studies to advocate for pharmaceutical development are needed. We also hope that the information offered in this review may encourage clinical studies to be conducted on this potential.