Influence of seasonality on phenol content and antioxidant and antimicrobial activities of the extract from the leaves of Schinus terebinthifolius (Aroeira-vermelha)

Abstract

Schinus terebinthifolius is widely used in traditional Brazilian medicine for its therapeutic properties, such as antimicrobial, antioxidant, and antifungal action. Although these properties are well studied, the influence of seasonality still needs to be fully understood. Thus, this study aims to evaluate the effect of seasonality on the content of phenolic compounds and the antioxidant and antimicrobial activities of the plant's leaves. Samples were collected in Salvador, Bahia, in July 2021 and January 2022, macerated in methanol, and partitioned into hexane and ethyl acetate, yielding hexane (STH) and ethyl acetate (STA) extracts. Total phenols, flavonoids, and tannins were determined by the Folin-Ciocalteau, AlCl₃, and FeCl₃ methods, respectively. The antimicrobial activity was evaluated using the broth microdilution method, and the antioxidant activity was assessed using the DPPH (1,1-diphenyl-2-picrylhydrazine) free radical scavenging method. The results obtained confirmed the antioxidant activity of winter and summer STA and winter STH. The inhibitory concentrations (IC50) were 0.028 mg/mL and 0.163 mg/mL for STA winter and STA summer, respectively. These fractions were the ones that presented the highest levels of total phenols and flavonoids. Of the STH fractions, only the winter one showed activity with IC50 of 0.875 mg/mL. Regarding the antimicrobial activity, all the summer season extracts showed activity against four of the five bacterial strains tested. STA summer demonstrated bactericidal and bacteriostatic activity, while STH winter showed bacteriostatic activity. Regarding the fungi tested, STH summer showed fungistatic and fungicidal activity against Candida albicans and C. glabrata.