Phytochemical and Bioactive Properties of Ochna afzelii and Steganotaenia araliacea from Northern Angola

Northern Angola preserves rich ethnobotanical knowledge of medicinal plants. However, Ochna afzelii and Steganotaenia araliacea, traditionally used in Bengo and Uíge, remain poorly characterized as potential sources of bioactive compounds for food applications. This study aimed to characterize their phytochemical profiles and evaluate the antioxidant activity, inhibition of lipid oxidation, and antibacterial activity of their extracts. The samples were cleaned, dehydrated, and ground, and aqueous leaf extracts were prepared. Total phenolic content, antioxidant activity, the ability to inhibit lipid oxidation and antibacterial activity against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli B and E. coli O157 were determined.

O. afzelii showed a total phenolic content of 4.74 mg/g of dry plant, with DPPH, FRAP, and ABTS TEAC values of 11.40, 158.2, and 2745.8 µmol Trolox/g of plant, respectively. S. araliacea showed a total phenolic content of 2.40 mg/g of dry plant, with DPPH, FRAP, and ABTS values of 22.76, 104.5, and 2717.1 µmol Trolox/g of dry plant, respectively. In the TBARS assay, S. araliacea exhibited an EC₅₀ of 6.0 µg/mL of dry extract, compared with 8.0 µg/mL for O. afzelii. Antibacterial activity was limited under the tested conditions, with no relevant inhibition zones observed for extracts of either species. Phytochemical analysis of the O. afzelii extract identified apigenin-C-acetylhexoside and chrysoeriol-8-C-hexoside-6-C-pentoside, both at an individual concentration of 2.8 ± 0.1 mg/g dry extract. In the S. araliacea extract, 3,5-di-O-caffeoylquinic acid (45 ± 1 mg/g dry extract), malonyl di-O-caffeoylquinic acid (11.3 ± 0.3 mg/g dry extract), and quercetin-acetylhexoside (8.9 ± 0.3 mg/g dry extract) were identified.

These findings contribute to the scientific valorisation of the ethnobotanical knowledge of Bengo and Uíge and suggest that O. afzelii and S. araliacea may represent valuable sources of natural compounds for future food applications, particularly as functional ingredients or natural alternatives to certain synthetic additives.