Anti-Inflammatory and Cytotoxic Compounds Isolated from Plants of Euphorbia Genus

Euphorbia is a large genus of the Euphorbiaceae family. Around 250 species of the Euphorbia genus have been studied chemically and pharmacologically; different compounds have been isolated from these species, especially diterpenes and triterpenes. Several reports show that several species have anti-inflammatory activity, which can be attributed to the presence of diterpenes, such as abietanes, ingenanes, and lathyranes. In addition, it was found that some diterpenes isolated from different Euphorbia species have anti-cancer activity. In this review, we included compounds isolated from species of the Euphorbia genus with anti-inflammatory or cytotoxic effects published from 2018 to September 2023. The databases used for this review were Science Direct, Scopus, PubMed, Springer, and Google Scholar, using the keywords Euphorbia with anti-inflammatory or cytotoxic activity. In this review, 68 studies were collected and analyzed regarding the anti-inflammatory and anti-cancer activities of 264 compounds obtained from 36 species of the Euphorbia genus. The compounds included in this review are terpenes (95%), of which 68% are diterpenes, especially of the types ingenanes, abietanes, and triterpenes (approximately 15%).


Introduction
Inflammation is a homeostatic defense of the body against any injurious stimulus, whether physical, chemical, or biological [1].It is characterized by the presence of pain, redness, swelling, heat, and loss of function, and it can be classified as acute or chronic.Acute inflammation is a protective response that disappears within minutes, hours, or a few days after the stimulus or injury.It is characterized by the release of phagocytes and mediators that act on endothelial cells, causing changes in vascular permeability and generating the migration of leukocytes and plasma proteins to produce edema.At this level, a generalized systemic reaction is triggered, and it is dynamic to resolve the inflammation.If unresolved, there is a risk that the inflammation could become chronic [2].
Chronic inflammation is long-term, lasting months to years, and it is characterized by the infiltration of macrophages, lymphocytes, and plasma cells into the injured tissue.It is a proliferation of fibroblasts and small blood vessels [2] producing pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), and IL-8, and they stimulate reactive oxygen species (ROS), which are involved in modulating inflammation and activating the transcription factor NF-κβ [3].
Currently, in the treatment of inflammatory problems, steroidal (SAIDs) and nonsteroidal anti-inflammatory drugs (NSAIDs) and disease-modifying antirheumatic drugs (DMARDs) are used.However, their constant or long-term use produces undesirable side effects on the renal, liver, gastric, cardiovascular, and central nervous systems [4].
The progress and permanence of inflammation are the reasons for most chronic diseases, and inflammation presents one of the major threats to the health and longevity of persons.Chronic inflammation is involved in several diseases, including, for example, Alzheimer's, type 2 diabetes, obesity, hypertension, and cancer [5].
Cancer is a disease where some cells of the body grow uncontrollably and can blowout to other organs of the body; this disease is caused by mutations, and the inflammation process produces oxidative stress, which causes damage to DNA and initiates signaling pathways, thus deregulating the cell cycle and increasing the risk of developing cancer [6].The most common treatment for cancer is chemotherapy, which produces side effects and can result in resistance to the compounds used [7].
Since ancient times, many cultures have used plants for therapeutic purposes as an important source of natural products for treating different health problems, such as inflammation and cancer.Recently, the research on medicinal plants has been increasing [8]; about 80% of chemotherapeutic drugs have been obtained from plants in addition to anti-inflammatory compounds [9].

Ethnobotany
The Euphorbiaceae family is one of the most diverse families of flowering plants of angiosperms.This family contains around 6745 species in 317 genera, distributed mainly in the tropics and subtropics of the world [10].In Mexico, Euphorbia species are found mainly in Nayarit, Veracruz, Chiapas, Michoacán, Oaxaca, Jalisco, Guerrero, Puebla, Sonora, Sinaloa, and Tamaulipas.Only about 250 species of the Euphorbia genus have been studied chemically and pharmacologically [11,12]; from these species, terpenes, flavonoids, alkaloids, coumarins, cyanogenetic glycosides, and mainly tannins have been isolated.Several reports show that some species have anti-inflammatory activity, which can be attributed to the presence of diterpenes, such as tiglians, ingenanes, and dafnanes.In addition, it was found that some diterpenes isolated from different Euphorbia species have anti-inflammatory and cytotoxic activity against some types of cancer [13][14][15].

Discussion
At present, the study of natural products obtained from medicinal plants continues to be of great interest because they provide a wide range of compounds with pharmacological activity against diseases, such as cancer, diabetes, and cardiovascular and chronic respiratory diseases, which, according to the World Health Organization (WHO), are the leading causes of mortality worldwide [84].Furthermore, these diseases involve acute and chronic inflammatory processes.For this reason, it is of great importance to conduct reviews of scientific studies that provide an overview of the molecules isolated from plants used in traditional medicine, such as those of the Euphorbia genus.In this review, 68 studies were collected and analyzed regarding the anti-cancer and anti-inflammatory effects of 264 compounds isolated from 36 species of the Euphorbia genus.The anti-inflammatory activity of 104 compounds was evaluated for NO inhibition on macrophages or BV-2cells stimulated with LPS using the Griess assay.Also, we found that compounds 97-107 have been investigated through vivo studies on ear edema in mice induced with TPA or paw edema induced with carrageenan or histamine.The cytotoxic activity of 147 secondary metabolites was evaluated against human cancer cell lines.Both activities, anti-inflammatory and cytotoxic effects, were evaluated only in 14 metabolites isolated from E. kansuensis and E. alatavica (49), E. kansui (50), E. lathyris (68,69,74,80,83,87), E. maculate and E. pedroi (95), E. nerifolia (116,117,118,119), and E. wallichii and E. fisheriana (136).
Some species of the genus Euphorbia produce latex, also known as "milky sap."These latexes are characterized by containing a variety of compounds with pharmacological activities [85].In Table 1 is shown that the latexes obtained from E. resinifera and E. umbellata were extracted with methanol and a solution of 1% H 2 SO 4 , respectively.From the methanol extract of E. resinifera, latexes were isolated Euphatexols C (126), Euphatexols D (127), Euphatexols E (128), Euphatexols F (129), and Euphatexols G (130); all of them had antiinflammatory activity (Table 2) [72].From the latex of E. umbellata was obtained Euphol (206); its cytotoxic activity was evaluated on the K-562 and HL-70 cancer cell lines (Table 3) [81].
Abietanes, rosanes, atisanes, beyeranes, and kauranes are characterized by three fused rings of six members, and some carbons are substituted with carbonyl or hydroxyl groups (264).Frequently, an olefin bond is found in the structure (Figure 20) [86].Tiglianes, daphnanes, and ingenanes are characterized by a tetracyclic fused ring.Tiglianes usually have a configuration trans of the fusion of rings A and B and cis for the fusion of rings B and C. Daphnane diterpenoids have a tricyclic skeleton and the fusion of the rings A and B and B and C is trans [86].Ingenanes diterpenes belong to the polycyclic diterpenoids related to daphnanes and tiglianes [87]; these diterpenes frequently contain hydroxyl and carbonyl groups and double bonds.
Lathyranes, jathropanes, and ingol are macrolides.Lathyranes diterpenes have a fused trycyclic system (5/11/3 members).Jathropanes have a bycyclo [9.3.0]pentadecane skeleton without a ring of cyclopropane.Ingol diterpenes are a subgroup of lathyranes Tiglianes, daphnanes, and ingenanes are characterized by a tetracyclic fused ring.Tiglianes usually have a configuration trans of the fusion of rings A and B and cis for the fusion of rings B and C. Daphnane diterpenoids have a tricyclic skeleton and the fusion of the rings A and B and B and C is trans [86].Ingenanes diterpenes belong to the polycyclic diterpenoids related to daphnanes and tiglianes [87]; these diterpenes frequently contain hydroxyl and carbonyl groups and double bonds.
These types of diterpenes show several pharmacological activities, some of which might be used clinically to treat health problems, such as cancer and inflammation [91].
Different researchers have found many diterpenes have anti-inflammatory activity through the inhibition of NF-κβ activation [86]; also, they diminish in macrophages stimulated with LPS, the production of TNF-α, NO, PGE2, the expression of COX-2, and iNOS mRNA [14].
For example, the factors L3 and L9 diminished the production of NO in LPS-stimulated macrophages by 61.85% and 63.68%, respectively.Also, both compounds had cytotoxic activity against BK (IC 50 values of 7.9 and 6.1 µM, respectively) and BK-VIN (IC 50 values of 8 and 5.7 µM, respectively) [58].The compounds 1, 2, 70, and 137 promoted the suppression of iNOS expression and consequently decreased inflammation [17,54,83].iNOS is the enzyme primarily responsible for the release of NO in inflammatory processes.
The compounds 18, 57, 61, and 69 suppressed NF-κβ, which is a light polypeptide gene enhancer in B cells produced and expressed by macrophages stimulated with LPS [53][54][55]60]; it promotes vasodilation and vascular permeability of blood vessels, facilitating the formation of edema and the recruitment of inflammatory cells around an injury [92].For this reason, the compounds that decreased the levels of this polypeptide are candidates to be used in the treatment of inflammation.
Cynsaccatol L (50) isolated from E. lathyris shows the highest effect on the inhibition of the production of NO for macrophages stimulated with LPS.This compound regulated the levels of TNF-α and IFN-7 and promoted the phagocytosis of macrophages of the M2 subtype [46] Cancer is a multifaceted ailment arising from mutations in cell proliferation.Interestingly, chronic inflammation has also been identified as a potential precursor to cancer in certain instances.The onset of cancer-promoting inflammation often precedes the formation of tumors.Notable examples of this connection can be found in certain conditions, such as Helicobacter-induced gastritis, chronic hepatitis, inflammatory bowel disease, and schistosomiasis-induced bladder inflammation.These conditions elevate the risk of developing several types of cancer, including, for example, colorectal, liver, stomach, and bladder cancer [93].
Many Euphorbia species contain compounds with cytotoxic activity.The mechanism of action of several types of diterpenoids has been investigated, and the results show that these compounds could have cytotoxic activity via induction of apoptosis through the suppression of IL-6-induced and STAT3 activation, the inhibition of topoisomerase II, and the impedance of NF-κβ activation [86].
The compounds factor L1 and Euphosorophane I were evaluated with tests other than cytotoxicity in cancer cell lines [51,75].Euphosorophane I (262) inhibited the function of transmembrane P-glycoprotein (P-gp), which has the function of an energy-dependent "drug pump."Its overexpression promotes multidrug resistance (MDR).This effect was tested on drug-resistant MCF-7/ADR cells; it was found that compound 262 exhibited a P-gp-mediated MDR reversal [75].
The anti-cancer activity of factor L1 was studied in in vivo and in vitro models.This molecule presented cytotoxic and antitumor activity downregulating DDR1 in the tumor of SHI mice.This compound avoids anti-liver metastasis.Factor L1, Euphylbenzoate, and Glutinol induced cell death through apoptosis [39,51,73].
Factor L2 had a potent cytotoxic activity on A549 and induced apoptosis via the mitochondrial pathway, promoting the release of cytochrome C and the activation of caspase 3 and 9 [94]

Methods
The literature search of documents and reviews on the anti-inflammatory and cytotoxic studies of the different species of Euphorbia was conducted in the PubMed, Springer, Science Direct, and Google Scholar online databases.The recovered information that is presented was published in the last 5 years.Only studies on isolated compounds were considered.Different in vivo models were used to establish anti-inflammatory activity.With respect to the cytotoxic activity, different in vitro colorimetric methods were used, as well as different cancer cell lines (murine, human, and resistant).Table 1 shows the species, the collection place, the part of the plant, and the bioactive extract studied to isolate the active compounds.

Conclusions
In summary, plants of the Euphorbia genus are a source of compounds with antiinflammatory and anti-cancer activities.Furthermore, different compounds shown in this review might lead to possible new therapies for inflammation and cancer to increase the options for the treatment of inflammatory diseases that afflict the world.Thirty-six species of Euphorbia were studied, and the specie that predominated was E. lathyris, which was researched in ten studies.
One hundred forty-one compounds included in this review have anti-inflammatory activity; one hundred forty-three natural products have anti-cancer effects; and ten molecules present both activities.

Table 2 .
The anti-inflammatory activity of the compounds obtained from 16 species of Euphorbia.

Table 3 .
The cytotoxic activity of the compounds obtained from 27 species of Euphorbia.

Table 3 .
The cytotoxic activity of the compounds obtained from 27 species of Euphorbia.
17. Structures of compounds isolated from E. lactea, E. lathyris, E. microsphaera, and E. neriifolia.Structures of compounds isolated from E. lactea, E. lathyris, E. microsphaera, and E. neriifolia.Structures of compounds isolated from E. pedroi and E. pekinensis.Structures of compounds isolated from E. pedroi and E. pekinensis.Structures of compounds isolated from E. pedroi and E. pekinensis.