Correlation of Total Phenolic, Flavonoid and Tannin Content of Bryophyllum pinnatum (Lam.) (Crassulaceae) Extract with the Antioxidant and Anticholinesterase Activities

Bryophyllum pinnatum is a perennial herb used in traditional medicine against varieties of ailments such as memory disorder. This study quantitatively estimated the total phenolic (TPC), total flavonoid (TFC) and total proautocyanidin (TPA) contents of extract and fractions of B. pinnatum and correlated them with its antioxidant and anticholinesterase activities. Methanolic extract of the dried leaves was partitioned into n-hexane, ethyl acetate and aqueous fractions. Total phenolic, flavonoids and proanthocyanidins content were estimated as gallic acid or quercetin equivalents. DPPH and nitric oxide scavenging activity as well as ferric reducing power assays were used to evaluate antioxidant activity, using 2,6-di-tert-butyl- 4-methylphenol (DDM) and ascorbic acid as standards. In vitro anticholinesterase activity was evaluated by Ellmann’s colorimetry assay with phsiostigmine (serine) and donepezil as positive control. The crude methanol extract had the highest phenolic, flavonoid and tannin content. The ethyl acetate fraction had the highest DPPH radical scavenging effect (IC₅₀ 0.004 mg/ml) while the aqueous fraction had the highest NO scavenging and ferric reducing effects with values of IC₅₀ 0.012 mg/ml and 0.007 mg/ml respectively. The ethyl acetate fraction had the best cholinesterase inhibitory effect (IC₅₀ 0.951 μg/ml AChE; 3.546 μg/ml BuChE). DPPH radical scavenging effect correlated strongly with total phenolic, flavonoids and proautocyanidins (r² 0.896, 0.651 and 0.619 respectively) while ferric reducing power showed weak correlation and NO scavenging as well as AChE inhibition had no correlation. The study shows DPPH radical scavenging could be due to the phenolic content while other class of compounds are responsible for the cholinesterase inhibition.