Background: In contrast to the several reports of alkaline extracts (Sasa-health, SE), no study of flavonoids from the leaves of S. senanensis has been reported. Four flavonoids were isolated from this plant species and their biological activities were investigated.
Materials and methods: Luteolin 6-C-β-D-glucoside [1], luteolin 7-O-β-D-glucoside [2], luteolin 6-C-α-L-arabinoside [3] and tricin [4] were extracted from the leaf of S. senanensis with methanol, partitioned with ethyl acetate, separated by Sephadex LH-20 and purified by high-performance liquid chromatography (HPLC). The structure was determined by ultraviolet (UV) spectra, high-resolution mass spectra (HR-MS) and nuclear magnetic resonance (NMR).
Results: The luteolin glycosides, 1-3 showed no cytotoxicity against the human normal oral cells and oral squamous cell carcinoma cell lines used up to 0.8 mg/ml, whereas 4 was highly cytotoxic. The luteolin glycosides 1-3 protected the cells from UV induced cytotoxicity, more efficiently than 4. The anti-HIV activity of 4 (Selectivity index, SI=27) was much higher than that of the luteolin glycosides (SI=2-7), but lower than that of SE (SI=40). The scavenging activity of 1-3 against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radicals was comparable with that of quercetin and, much higher than that of 4.
Conclusion: The luteolin glycosides from S.senanensis show several new biological properties distinct from tricin and the anti-UV activity of the luteolin glycosides may be derived from their radical scavenging activity.