Secondary metabolite contents and antimicrobial activity of leaf extracts reveal genetic variability of Vernonia amygdalina and Vernonia calvoana morphotypes

Abstract

Vernonia species (Asteraceae) are indigenous medicinal and food leaf vegetables commonly consumed in some African countries like Cameroon where they constitute a staple dish called “ndolé.” Previous studies have demonstrated the nutritional importance of Vernonia, but there is little knowledge of their agronomic value and genetic potentials. Wide genetic variability in the genus has been established earlier through the study of its pollen. However, to the best of our understanding, no such study has been undertaken on the genetic variability of Vernonia with respect to its secondary metabolites. This study was therefore aimed at evaluating the genetic variability of Vernonia amygdalina (VAA and VALF) and V. calvoana (VCAB, VCAV, VCSB, and VCSV) morphotypes in 2016 based on secondary metabolite content and antimicrobial properties. This involved phytochemical analysis by HPLC/MS for the detection of alkaloids, flavonoids, phenols, and tannins in leaves from each of the six genotypes. Results showed that all tested genotypes are rich in phenols (18 analyzed), flavonoids, and tannins with, VAA richer in phenols (206.1 ± 3.12 µg/g of dry extract), followed by VCAV (197.9 ± 18.03 µg/g). The lowest level of flavonoid was found in VCSV (81.6 ± 7.21 µg/g), while the highest was from VCAB (132.8 ± 31.5 µg/g). VCSV (56.3 ± 4.08 µg/g) had the lowest level of tannins, while VCAB (97.8 ± 23.8 µg/g) had the highest levels. Assessment of antimicrobial activity of leaf extracts from the six genotypes was done by culture on Mueller Hinton (MH) agar and MH broth agar for bacteria and in Sabouraud dextrose agar and Sabouraud dextrose broth media for fungi, respectively. All morphotypes exhibited inhibitory activity on bacteria except VAA, with isoquercetin characteristic of VCSV. Chemotaxonomic analyses of Vernonia morphotypes highlighted the genetic diversity within species and variability of antimicrobial properties of ethanolic leaf extracts among morphotypes. These results provide baseline data in the valuation of genetic resources and the establishment of improvement programs.

Antimicrobial and Antibiotic-Resistance Reversal Activity of Some Medicinal Plants from Cameroon against Selected Resistant and Non-Resistant Uropathogenic Bacteria

“…Similarly, ethanolic extracts of L. vulgare and V. amygdalina showed a broad-spectrum antimicrobial activity against all the tested pathogens. This could be ascribed to the richness of these extracts in phytochemicals such as saponins, sesquiterpenes, flavonoids, steroid glycosides, and lactones [20] for which recent studies reported its antibacterial activity [21]. Amongst leaves extracts, those derived from M. oleifera were more actives against the bacterial strains E. coli ATCC 25922 and S. aureus ATCC 6538 while extract from L. vulgare leaves was more active against C. albicans ATCC 10231.…”

“…It has also been reported to have antioxidant, anti-inflammatory, antitumor, antimicrobial, hepatoprotective and anti-arthritic properties [14][15][16]. V. amygdalina (known in Cameroon under the popular name of Ndolè) have been reported to have anticancer and antitumor activity [17,18]; antihepatotoxic activity [19]; hypoglycemic activity [20]; antibacterial activity [21]; anti-inflammatory [22] as well as antioxidant property [23]. Moreover, C. citratus (lemongrass) is widely used as a tea and is rich in minerals, vitamins, macronutrients (including carbohydrate, protein, and small amounts of fat) and its leaves are a good source of various bioactive compounds such as alkaloids, terpenoids, flavonoids, phenols, saponins and tannins that confer C. citratus leaves pharmacological properties such as anti-cancer, antihypertensive, anti-mutagenicity, anti-diabetic, antioxidant, anxiolytic, anti-nociceptive and anti-fungal [24].…”

“…Moreover, C. citratus (lemongrass) is widely used as a tea and is rich in minerals, vitamins, macronutrients (including carbohydrate, protein, and small amounts of fat) and its leaves are a good source of various bioactive compounds such as alkaloids, terpenoids, flavonoids, phenols, saponins and tannins that confer C. citratus leaves pharmacological properties such as anti-cancer, antihypertensive, anti-mutagenicity, anti-diabetic, antioxidant, anxiolytic, anti-nociceptive and anti-fungal [24]. Like C. citratus, all plants investigated in this study have various phytocompounds such as terpenoids and xanthones products, alkaloids (such as protoberberines and phenanthrene alkaloids), aporphines, zeatin, quercetin, β-sitosterol, caffeoylquinic acid and kaempferol, saponins, sesquiterpenes, flavonoids, steroid glycosides, and lactones [9,13,20,25,26]. These multiple compounds make these plants an exploitable source for the development of new antimicrobials.…”

Galleria mellonella as a novel eco-friendly in vivo approach for the assessment of the toxicity of medicinal plants

“…In Cameroon, V. amygdalina is known under the name of Ndolè and is included in the composition of the national popular dish which bears the same name. The presence of polyphenols, vitamins and mineral salts make the plant useful in human diets [25,26]. V. amygdalina is very rich in phytochemicals such as saponins, sesquiterpenes, flavonoids, and steroid glycosides (vernosides), lactones [26] and several studies reported that it has anticancer and antitumor activity [27,28]; antihepatotoxic activity [29]; hypoglycemic activity [26]; antibacterial activity [30]; anti-inflammatory [31] as well as antioxidant property [32].…”

Screening of antimicrobial activity of aqueous and ethanolic extracts of some medicinal plants from Cameroon and assessment of their synergy with common antibiotics against multidrug-resistant uropathogenic bacteria

“…It has also been reported to have Antioxidant, antiinflammatory, antitumor, antimicrobial, hepatoprotective and anti-arthritic properties (Ray et al, 2015; Arulselvan et al, 2016;Saleem et al, 2020). V. amygdalina (known in Cameroon under the popular name of Ndolè) have been reported to have anticancer and antitumor activity (Hasibuan et al, 2020;Joseph et al, 2020); antihepatotoxic activity (Yedjou et al, 2018); hypoglycemic activity (Dumas et al, 2020); antibacterial activity (Egbuonu and Amadi, 2021); anti-inflammatory (Wang et al, 2020) as well as antioxidant property (Alara and Abdurahman, 2021). Moreover, C. citratus (lemongrass) is widely used as a tea and is rich in minerals, vitamins, macronutrients (including carbohydrate, protein, and small amounts of fat) and its leaves are a good source of various bioactive compounds such as alkaloids, terpenoids, flavonoids, phenols, saponins and tannins that confer C. citratus leaves pharmacological properties such as anti-cancer, antihypertensive, anti-mutagenicity, anti-diabetic, anti-oxidant, anxiolytic, anti-nociceptive and anti-fungal (Muala et al ., 2021).…”