Medicinal properties of Ocotea bullata stem bark extracts: phytochemical constituents, antioxidant and anti-inflammatory activity, cytotoxicity and inhibition of carbohydrate-metabolizing enzymes

Abstract

Objective: This study evaluates the phytochemical constituents, antioxidant and anti-inflammatory activity, cytotoxicity, and inhibitory activity against carbohydrate metabolism of extracts from Ocotea bullata stem bark.

Methods: Hexane, ethyl acetate, methanol and water were used to extract the air-dried sample. The phytochemical investigation and antioxidant assays were carried out on the extracts using standard procedures. The antidiabetic and anti-inflammatory potentials were evaluated using α-amylase, α-glucosidase and 5-lipoxygenase enzymes respectively. Vero cells were employed to determine the cytotoxicity of the extracts.

Results: The ethyl acetate extract showed higher phenolic contents (8.97 mg/g gallic acid) while methanol displayed higher flavonoid (36.06 mg/g quercetin) and flavonol (153.44 mg/g rutin) contents than other extracts. Hexane extract had the greatest capacity to scavenge 1,1-diphenyl-2-picryl-hydrazyl (0.19 mg/mL), hydroxyl (25.77 mg/mL) and 2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (0.07 mg/mL) radicals, while ethyl acetate extract exhibited stronger inhibition (P < 0.05) against superoxide anion (0.41 mg/mL) and ferric ion-reducing power (2.36 mg/mL) compared to other extracts and standards. Aqueous extract (27.02 mg/mL) exhibited strong metal-chelating activity (P < 0.05) compared to other extracts and gallic acid. The aqueous extract demonstrated the greatest inhibition of α-glucosidase (1.45 mg/mL) and α-amylase (2.43 mg/mL) compared to other extracts and acarbose. There were no significant differences (P < 0.05) in half-maximum inhibitory concentration (IC₅₀) values of all tested extracts and indomethacin in the inhibition of 5-lipoxygenase activity. The aqueous extract was nontoxic to Vero cells with an IC₅₀ value of 0.38 mg/mL.

Conclusion: O. bullata stem bark contains active phytochemicals with diverse pharmacological potentials that could be beneficial in managing diabetes and inflammation.

Keywords: Anti-inflammatories; Antidiabetics; Antioxidants; Cytotoxicity; Ocotea bullata.