Isolation of squarrosal and squarrosol compounds from methanol root extract of Ruellia squarrosa (Acanthaceae)

Purpose: To identify, characterize and structurally elucidate bioactive compounds from root of Ruellia squarrosa.Methods: One kilogram of crude Ruellia squarrosa root was shade dried for 14 days, ground to a fine powder and subjected to a methanol extraction. The resultant extract underwent column chromatography for further purification. The isolated compounds were subjected to ultraviolet spectroscopy (UV), infra-red (IR), proton nuclear magnetic resonance (1H-NMR), 13C–NMR and high resolution electron ionization mass spectrometry (HR-EI-MS) for the identification, characterization and structural elucidation of bioactive compounds. The most active compounds were tested for anticancer activities against human prostate cancer cell.Results: Two active compounds, squarrosol and squarrosal, were obtained with half-maximal inhibitory concentration (IC50) of 15.6 and 26.6 μg/mL, respectively, against human prostate cancer cell lines. Squarrasol showed a significantly (p < 0.05) greater inhibition of cell proliferation than the same dose of squarrasal.Conclusion: These findings suggest that extracts of Ruellia squarrosa containing the bioactive compounds, squarrosol and squarrosal, can potentially be developed for the treatment of human prostate cancer.