Phytochemical composition, antioxidant activity and antibacterial efficacy of methanolic extracts of by-products of three varieties of Persea americana Mill. grown in Morocco

Abstract

This study aims to study the phyto-chemical composition of the methanolic extracts of the fruit by-products (seeds and peels) of three varieties of Persea americana, in order to evaluate their antioxidant and antibacterial activities. The contents of total polyphenols, flavonoids and condensed tannins were determined respectively by the Folin-Cio-calteu methods of the aluminum chloride reagent and vanillin. The antibacterial activity of the extracts was assessed using the diffusion technique on discs, and the antioxidant capacity was assessed using the free radical scavenging method DPPH. The results of phytochemical screening showed a richness in secondary metabolites on the seeds and peels of all the varieties studied, in particular polyphenols, free tannins, alkaloids, proteins, and saponosides. Regarding the quantitative analysis, the seeds of the Hass variety showed high TPC contents (108.026 ± 0.71 mg of GAE/g) in TFC (44.23 ± 0.91 mg of QE/g) and Tannins (357.59 mg of CE/g), for the peels, Zutano showed the high-est TPC values (88.51 ± 0.36 mg of GAE/g) in TFC (39.856 mg of QE/g) and in tannins (216 ± 2.03 mg of CE/g), while Fuerte has moderate concentrations in both parts for all dosages. In terms of antibacterial activity, a marked effectiveness has been found against Gram-positive bacteria, and only against E. coli among Gram-negative ones. For antioxidant activity, the Zutano variety showed the best antioxidant activity (IC₅₀ = 21.268 µg/ml for the seed and IC₅₀ = 33.182 µg/ml for the peels). According to these results, methanolic extracts from seeds and peels represent a potential source of bioactive compounds that must be valued for use in different fields.