1. Introduction
Plants are used in traditional medicine to treat a wide range of ailments. These medicinal-aromatic plants (MAPs) are well known for their biological activity. The World Health Organization estimates that over 80% of the global population still has confidence in conventional and folk medicine, mostly based on herbal remedies [
1,
2]. Herbs and plant-derived products have a long history of safe use as natural products in the treatment of various diseases [
3].
Morocco is known for its beneficial geographical location as a country with Mediterranean and Atlantic coasts, which has contributed to an interesting plant diversity [
4,
5]. The Asteraceae family is the largest flowering herb family, with over 1700 genera and 34,000 species worldwide. It involves several plants with medicinal values, such as chamomile, wormwood, and dandelion, among others [
6].
Studies have shown that some Asteraceae plants have many biological properties, such as antioxidant [
7], antifungal [
8], antibacterial [
9], anti-inflammatory [
10], and anticancer activities [
11].
Cladanthus mixtus (L.) Chevall. (Moroccan chamomile or simple leaved chamomile, synonymous with
C. mixtus (L.) Oberpr. and Vogt.,
Anthemis mixta L.,
Chamaemelum mixtum (L.) All., and
Ormenis mixta subsp.
mixta) belongs to the Asteraceae family [
12]. This traditional medicinal plant is widespread in Morocco and in the northern and eastern zones of the Mediterranean basin. The flowers and leaves of
C. mixtus are the most commonly used parts as an infusion to treat various diseases [
13,
14]. Furthermore,
C. mixtus is used by therapists and herbalists as an antispasmodic, analgesic, antiallergic, anti-inflammatory, carminative, digestive, febrifuge, fungicide, vermifuge [
15], antioxidant agent [
16], and anticancer treatment [
11].
In a previous study by El Mihyaoui et al. [
11], the HPLC-MS analysis of methanolic extracts from
C. mixtus revealed the presence of 23 phenolic compounds identified in the flowers and 24 compounds in the leaves, stems, and roots extracts; the GC-MS analysis of methanolic extracts without derivatization showed that
C. mixtus is rich in biomolecules, including terpenoids, alcohols, esters, alkanes, fatty acids, organic acids, benzenes, phenols, ketones, sterols, carbonyls, amines, and other groups.
Plants can produce many diverse bioactive compounds, and several factors can affect the yield of these compounds, such as different extraction solvents and techniques as well as the particular isolation and purification of bioactive molecules [
17].
The aim of this work is to investigate the chemical composition of methanolic extracts from different plant organs (flowers, leaves, stems, and roots) of wild Moroccan C. mixtus and to evaluate their biological activities, including antioxidant, antibacterial, and antifungal properties. To the best of our knowledge, this is the first comparative research study on the chemical characterizations and biological activities of different C. mixtus organs (flowers, leaves, stems, and roots) from northern Morocco (Tangier-Tetouan-Al Hoceima region).
3. Discussion
Plant extracts containing phytochemicals are increasingly marketed as products with a positive impact on the human health system. This work aimed to characterize the metabolites of four organs from C. mixtus and evaluate their antioxidant, antibacterial, and antifungal activities.
Methanolic extracts of
C. mixtus flowers showed the highest content of polyphenols (36%), followed by flavonoids (42%) (
Figure 6). Polyphenol contents were similar in roots and stems (22%), followed by leaves (20%). For flavonoids, the stems showed a content close to that of the leaves (23% and 21%, respectively), followed by the roots (14%).
The total phenolic content of the
C. mixtus flower extract found in this work (30.55 mg GAE/g DW) is slightly higher than that found in the flower extract of a similar study with Italian
Matricaria chamomilla (2689.2 mg GAE/100 g DW) [
18] and much higher than a study with Egyptian
M. chamomilla (3.7 mg GAE/g DW) [
19] and a commercial
M. chamomilla product from the United Arab Emirates (21.4 mg GAE/g DW) [
20].
In a previous study, aerial part extracts of
C. mixtus (obtained from Bouznika, Morocco) presented a total phenolic content of 19.5 mg GAE/g DW in a methanolic extract and 38.2 mg GAE/g DW in an aqueous extract [
21], showing a lower content than that found in current research (65.75 mg GAE/g DW). Elouaddari et al. [
21] also reported that in aerial part extracts of
C. mixtus, the total flavonoid content was 2.7 and 3.2 mg QE/g DW in aqueous and methanolic extracts, respectively. In this investigation, our estimation showed a much greater amount of flavonoid content (53.61 mg QE/g DW) (
Table 1) than in the aforementioned study by Elouaddari et al. [
21]. The differences in extraction methods and the solvent and timing used may influence the composition of polyphenols, flavonoids, and other compounds and therefore also affect their biological activities.
In the present study, we applied the endpoint method developed by Arnao et al. [
22]. This technique uses 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) as a chromogen to estimate total antioxidant activity. It is a robust method, that is widely used and applied to various biological samples [
23]. Although this method was originally developed for the study of plant foodstuffs, it can also be used to characterize plant extracts [
16]. The ABTS
·+ chromogen used in our method was compared to another widely used radical chromogen, which is 2,2-diphenyl-1-picrylhydrazyl (DPPH
·). Furthermore, the extraction method and the solvent used can influence the composition of polyphenols, flavonoids, and other compounds and therefore also affect the antioxidant activity [
19,
24].
Zeroual et al. [
25] showed that methanolic extracts of
C. mixtus flowers had the highest free radical scavenging activity (IC
50 = 55.50 µg/mL), followed by the ethanolic extract (IC
50 = 121.5 µg/mL), ethyl acetate (IC
50 = 240.9 µg/mL), and n-hexane (IC
50 = 259 µg/mL). Similarly, the DPPH test showed that methanolic extracts of chamomile flowers (
Matricaria chamomilla) had the strongest antiradical power (IC
50 = 0.0022 µMoles) compared to ethanolic, diethyl ether, and hexane extracts [
19]. In contrast, methanolic extracts of the aerial part of
C. mixtus showed lower antioxidant activity than the aqueous extract by DPPH and ABTS tests [
21].
Furthermore, the choice of extraction organ plays an important role in antioxidant activity. In our study, we chose to separate the plant organs (flowers, leaves, stems, and roots) to compare their antioxidant activity. Methanolic extracts of the roots showed the best activity with ABTS, while the flowers showed a better result with DPPH. On the other hand, the leaves of C. mixtus showed the lowest activity in both tests.
A correlation analysis was carried out to study the relationship between the phenolic and flavonoid contents of the extracts and their antioxidant activities (
Table 12). Methanolic extracts of stem, leaf, and flower showed a very significant positive correlation between the content of phenolics and the antioxidant activity by the ABTS (r² = 0.93,
p < 0.05) and DPPH (r
2 = 0.94,
p < 0.05) tests. These organs also showed a strong correlation between their total flavonoid content and antioxidant activity by the ABTS (r² = 0.89,
p < 0.05) and DPPH (r
2 = 0.90,
p < 0.05) tests.
The ability of flavonoids to act as in vitro antioxidants has been the subject of several studies in recent years, and important structure-activity relationships for antioxidant activity have been established [
26,
27]. Almost all flavonoid groups can act as antioxidants, but it has been reported that flavones and catechins appear to be the most potent flavonoids in protecting the body against reactive oxygen species [
28].
Moreover, many studies have reported the benefits of phenolic compounds, such as vanillin, that have antioxidant and antidepressant activities and neuroprotective, antimutagenic, and anticarcinogenic effects [
29].
Based on the GC-MS analysis, the present research reveals that derivatized methanolic extracts from
C. mixtus contain carbohydrates, lactones, fatty acids, organic acids, amino acids, terpenoids, alcohols, phenolics, alkanes, and other compounds, with carbohydrate compositions in abundance. Comparing these results with others obtained of methanolic extracts from the same plant without derivatization [
11], we found that the flower extracts were dominated by fatty acids (27.86%), leaf extracts by terpenoids (46.20%), stem extracts by esters (30.11%), and root extracts by alcohols (24.49%) and esters (21.91%). The choice of the derivatization technique was made to improve and increase the volatility, sensitivity, thermal stability, greater selectivity, and separation behavior of the analytes [
30]. Another study on aqueous extracts of two Moroccan chamomiles,
C. mixtus and
M. chamomilla, discovered the presence of alkaloids, terpenoids, saponins, flavonoids, and tannins, but not anthraquinones [
31].
Elouaddari et al. (2019) [
32] examined the chemical composition and biological activities of
C. mixtus essential oils (EOs). According to the authors review, a total of 264 compounds constitute the EOs of
C. mixtus, which vary greatly depending on diverse parameters, including geographies, plant parts, extraction methods, and ecological factors. The distribution of these chemicals is as follows: oxygenated monoterpenes (30–45.3%), sesquiterpene hydrocarbons (14–33.9%), monoterpene hydrocarbons (15–24.5%), sesquiterpenes (4–11.7%), and others (traces–4.5%). Many properties, including antimicrobial, anticorrosive, and cytotoxic activity against human cervical cancer cell lines, are caused by these biomolecules.
Our results of HPLC-MS analysis reported in the previous study [
11] showed that the different methanolic extracts of the
C. mixtus plant are very rich in glycosides and aglycones (luteolin, apigenin, luteolin-7-
O-glucoside, apigenin-7-glucoside, quercetin, rutin, naringin, catechin, vanillin, kaempferol, and isorhamnetin) and phenolic acids (gallic, protocatechuic, chlorogenic, salicylic, p-hydroxybenzoic, caffeic, vanillic, syringic, methyl paraben, rosmarinic, p-coumaric, and ferulic acids). The presence of phenolic compounds and flavonoids may contribute to the activity of the extracts [
33]. Flavonoids, such as epicatechin and rutin, have been reported to be powerful radical scavengers [
28]. The scavenging ability of rutin may be due to its inhibitory activity on the xanthine oxidase enzyme [
28]. We revealed the presence of rutin in all extracts of
C. mixtus with interesting values, and the highest value was detected in
C. mixtus flowers (673.12 µg/g DW) [
11].
Additionally, the antimicrobial activities of natural products have attracted much attention due to the increasing incidence of pathogens that have become drug-resistant [
34]. In this study, the antibacterial activity of methanolic extracts of the flowers, leaves, stems, and roots of
C. mixtus was tested against
S. aureus and
E. coli strains isolated from clinical samples.
C. mixtus extracts exhibited antibacterial activity against the two selected strains, with the best result obtained with the leaf extract. The other organs showed almost the same activity against
E. coli.However, extracts are more effective against Gram-positive bacteria than Gram-negative bacteria. This difference in sensitivity is due to membrane permeability. Gram-negative bacteria have a complex and rigid membrane rich in lipopolysaccharide, which can limit the passage of antimicrobial constituents [
35].
The antibacterial activity of
Matricaria chamomilla extract (Asteraceae family) from Djibouti was investigated [
36]. Methanolic extracts of
M. chamomilla leaves showed higher antibacterial activity against
E. coli (MIC and MBC = 25 µg/mL) compared to
S. aureus (MIC and MBC = 100 µg/mL).
Concerning the antifungal activity, against
C. albicans and
A. fumigatus,
C. mixtus extracts appeared to be less effective, and
A. fumigatus was the most resistant (MIC and MFC > 40 mg/mL). In another report, the antifungal activity of the aerial part (leaves and flowers) of
M. chamomilla extracts (aqueous, methanol, and chloroform) was studied against
C. albicans and
Fusarium spp., and the results showed that the extracts had no effect on the fungal strains tested [
37]. In reverse, methanolic extracts of
Montanoa sp. and
Schistocarpha sinforosi Cuatrec. from the Asteraceae family showed moderate activity against
C. albicans (MICs = 0.62 and 2.50 mg/mL, respectively) [
38].
In a study reported by Mekonnen et al. [
39], the essential oil from
M. chamomilla flowers had no inhibitory effect against all strains of
Trichophyton and
Aspergillus. Comparing these results with the present study, all the methanolic extracts of
C. mixtus gave very good results against
T. rubrum.
Accordingly, it can be inferred from our results that the extracts of both plants showed antibacterial and antifungal activity. This can be explained by their chemical composition, which is rich in phenolic acids and flavonoids. They are also very rich in terpenoids, fatty acids, organic acids, esters, and ketones [
11].
Protocatechuic acid was isolated from the aerial parts of
Centaurea spruneri of the Asteraceae family to test its antibacterial activity [
40]. The MIC and MBC values against
S. aureus,
E. coli,
Bacillus cereus,
Micrococcus flavus,
Listeria monocytogenes,
Pseudomonas aeruginosa,
Proteus mirabilis, and
Salmonella typhimurium were between 100 and 400 mg/L. Several studies have revealed that other phenolic compounds have antimicrobial activities, such as ellagic acid [
41], gallic acid [
42,
43], and p-hydroxybenzoic acid [
44].
Overall, the findings of the present work demonstrated that all extracts of C. mixtus organs exhibited good antioxidant and antimicrobial activities, and results differed from one organ to another. Therefore, the extracts of the plant materials studied could be recommended as a source of pharmaceutical materials necessary for the preparation of new antioxidant and antimicrobial agents.