Phytochemical Composition, In vitro Antioxidant and Antimicrobial Activities of Methanol extract of Cheese Wood (Alstonia boonei) Leaves collected from Benin City, Nigeria

Abstract

The Cheese wood (Alstonia boonei) tree, known as Egbu-ora in Igbo, Ahun in Yoruba, Ukpukunu in Urhobo and Ukhu in Edo, is a widely distributed plant in the lowlands and rain-forest areas of Nigeria. It has been listed in the African Pharmacopoeia as an antimalarial drug and a traditional medicine for the treatment of fever, painful micturition, insomnia, chronic diarrhoea, and rheumatic pains as antivenom for snake bites and in the treatment of arrow poisoning. This work aims to investigate the phytochemical composition, in vitro antioxidant, and antimicrobial activities of methanol extract of cheese Wood (Alstonia boonei) leaves collected from Benin City, Nigeria. This study investigated the phytochemical composition, antioxidants, and antimicrobial activities of methanol extract of the Alstonia boonei leaves using standard methods. The phytochemicals present in Alstonia boonei are flavonoids, phenols, saponins, terpenoids, tannins, alkaloids, proanthocyanidins, glycosides, steroids and phytosterols, the in-vitro antioxidant was accessed using DPPH radical scavenging assay, reducing power assay, ferric reducing antioxidant potential and Nitric Oxide inhibition. The antimicrobial activity was evaluated using the disk diffusion method. The total phenolic, proanthocyanidin, flavonoids and tannins were determined using standard methods. The methanolic extract of A. boonei was shown to be highest in total phenol, flavonoid, and tannin and showed moderate consideration in proanthocyanidins. The methanolic leaves extract of A. boonei has 50% inhibition concentration IC₅₀ values for the radical scavenging activity of (64.47µg/mL), significantly higher than that of ascorbic acid (8.10 µg/mL). The reducing power assay showed that the standard ascorbic acid has better-reducing power when compared with A. boonei. However, A. boonei showed a marked increase at higher concentrations of (800 and 1000 µg/mL), and it also showed that A. boonei is a better nitric oxide inhibitor when compared with the standard gallic acid. The antimicrobial assay showed that A. boonei has better antifungal activity when compared to its antibacterial activity.