Determination and comparison of phenolic compound content and antioxidant activity of selected local Zimbabwean herbal teas with exotic Aspalathus linearis

• We identify five underutilised herbal teas consumed in Zimbabwe
• We compare phenolic composition and antioxidant activity with A. linearis (Rooibos™)
• Some herbs under study have higher phenolic content and some lower than Rooibos™
• All herbal teas under study have safe tannin content
• Zimbabwe herbal teas exhibit antioxidant activity comparable to A. linearis

Phenolic compounds have several biological effects such as anti-inflammatory, bactericidal and antioxidant properties due to their ability to neutralise free radicals. The aim of the study was to determine total phenolic content and antioxidant activities of Zimbabwean indigenous herbal teas and comparing them with Aspalathus linearis (Rooibos™), a commercial South African herbal tea. Plant leaves of Myrothamnus flabellifolius, Fadogia ancylantha, Lippia javanica, and Ficus sycamore and a concoction of Adansonia digitata fruit pulp, seed and fibre were analysed. Total phenolic content was determined using the Folin-Ciocalteau method. The butanol–HCl assay was used to determine condensed tannin content. Antioxidant properties were determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), reducing power and inhibition of phospholipid peroxidation assays. F. sycamore had the highest total phenolic content (14.02 ± 0.01 g GAE/100 g) while A. digitata fruit pulp mixture had the lowest (0.79 ± 0.28 g GAE/100 g). The highest tannin content was found in F. sycamore (1.98 ± 0.12 g/100 g and the lowest was in L. javanica (0.1174 ± 0.01 g LE/100 g). Only F. sycamore exhibited higher antioxidant activity than A. linearis in all antioxidant assays whereas activity in other herbal teas was interchangeably higher or lower depending on antioxidant assay carried out.