Phytochemical content, antidiabetes, anti-inflammatory antioxidant and cytotoxic activity of leaf extracts of Elephantorrhiza elephantina (Burch.) Skeels

Traditionally Elephantorrhiza elephantina is used in Southern Africa for treating ailments with over utilisation of the roots, placing the plant on the Red Data List. Consequently, the leaf is proposed as alternative for preservation and sustainable use. However, there is a dearth of information on the leaves’ biological activity and no report on the plants’ antidiabetic activity. The dried leaf extracts of E. elephantina (acetone, ethanol, cold water and hot water) were investigated for polyphenolic content, antioxidant, anti-inflammatory, antidiabetic and cytotoxic activities, using standard methods. The phenolic and flavonoid contents of the ethanol extract (292.71 ± 1.19 mg gallic acid equivalent (GAE)/g extract) and (55.38 ± 0.98 mg quercetin equivalent (QE)/g extract) respectively were the highest. In addition, the inhibition of α-amylase activity by the ethanol extracts (58.72 ± 0.40%) was the strongest. Furthermore, the ethanol extract was the least cytotoxic (LC₅₀ ˃1000 µg/mL) against H4IIE liver and differentiated C2C12 muscle cells (myotubules). However, for the other assays, the hot water extract was the most active. The hot water extract in a concentration dependent manner stimulated the highest C2C12 glucose utilisation activity in addition to exhibiting the strongest antioxidant [IC₅₀ of 20.45 ± 4.64 µg/mL (ABTS) and 38.09 ± 1.51 µg/mL (DPPH)] and anti-inflammatory (IC₅₀ of 20.88 ± 1.21 µg/mL) activities. Water and alcohol are used in preparing herbal remedies in traditional practice, indicating the significance of the results. To the best of our knowledge, this is the first study reporting the biological activities of E. elephantina leaf extracts.