Antioxidant and cytotoxic properties of Senna alata and Senna podocarpa leaf extracts

This study determines the antioxidant and cytotoxic potential of hydromethanolic leaf extract (HMLE) of Senna alata and Senna podocarpa, which are herbs commonly used in southern Nigeria, to treat a number of diseases (Okpuzor et al., 2004; Faruq et al., 2010) including sickle cell anemia and diabetes mellitus, which are characterised by oxidative stress (Vincent et al., 2004; Nur et al.,2011). Hydromethanolic leaf extracts were prepared by reflux, and total phenolics, flavonoids and tannin contents were determined using standard assays (Abdel-Hameed, 2009). The in-vitro antioxidant activities of the methanolic extracts were evaluated by assessing the total antioxidant capacity, total reducing power, DPPH radical scavenging activity (DRSA) as well as their DNA protection ability. The WST-1 cytotoxicity test was performed using K562 cell line. The results showed that Senna podocarpa HLME had a significantly higher flavonoid, tannin and phenolic content when compared to S. alata HLME, but S. alata HLME exhibited a significantly higher total antioxidant capacity. The reductive capability of Gallic acid > S. podocarpa HMLE > S. alata HMLE. The DRSA increased with increasing concentrations of both HLMEs and gallic acid. The DRSA of S. alata HMLE was more pronounced than that of S. podocarpa HMLE but weaker than the control gallic acid. The HMLE of S. podocarpa exhibited a dose dependent DNA protection activity, while the HMLE of S. alata at 10 µg/ml and 1000 µg/ml exhibited pro-oxidant activity, but 100 µg/ml showed DNA protection activity. Cytotoxicity was displayed by the HLME of S. alata and S. podocarpa and the CC₅₀ values were 104.5 ± 3.35 µg/ml and 131.8 ± 1.67 µg/ml respectively. The herbal control drug Nicosan had a CC₅₀ value of 115.3 ± 1.99 µg/ml. The hydromethanolic leaf extracts of S. alata and S. podocarpa have potent antioxidant properties, but both extracts were cytotoxic to the K562 leukaemia cell line.