Antioxidant and antibacterial activity of aqueous, ethanolic and acetonic extracts of Pimenta dioica L. leaves

The aim of the present work was to evaluate the antioxidant and antibacterial activity of crude extracts (aqueous, ethanolic, and acetonic) of Pimenta dioica L. leaves collected in Tabasco, México. The following tests were carried out: total phenols (Folin-Ciocalteu assay), antioxidant activity (DPPH, ABTS, and FRAP methods), and antibacterial activity (disc diffusion and minimum inhibitory concentration techniques) using Gram-positive and Gram-negative bacteria. To identify compounds in the extracts, UHPLC-QToF was utilised. The acetonic extract (AE) yielded the highest phenolic content (626.29 ± 28.11 mg GAE/g dry extract, p < 0.05). The phenolic content of the aqueous (WE) and ethanolic extracts (EE) (488.29 ± 15.56 and 516.35 ± 4.96 mg GAE/g dry extract, respectively) did not show a significant difference. Likewise, AE yielded the highest antioxidant activity of 52.26 ± 11.74 µg/mL (IC₅₀), 116.90 ± 10.82 µg/mL (IC₅₀), and 7.52 ± 0.16 mM TE/g dry extract for DPPH, ABTS, and FRAP assay, respectively. Again, the EE and WE did not show a statistical difference for the DPPH and ABTS assays, while the antioxidant activity with the FRAP assay showed statistically different results for the three extracts in the order of AE > EE > WE. In addition, all three extracts showed antibacterial activity, with B. cereus and S. aureus (Gram-positive bacteria) more sensitive than S. Typhimurium and E. coli (Gram-negative bacteria); however, the minimum inhibitory concentrations were high with respect to the positive control (amikacin). Using the HPLC analysis, it was possible to detect and confirm the presence of some compounds such as phenols, flavonols, triterpenes, sapogenins, and polyalcohol in AE, EE, and WE . The antioxidant activity was closely related to the content of total phenols, although not all phenolic compounds had antibacterial activity. Extracts of P. dioica leaves are a source of phenolic compounds and can be used as antioxidant agents in the food, cosmetic, and pharmaceutical industries.