Organosulfur Compound Identified from Striga angustifolia (D. Don) C.J. Saldanha Inhibits Lung Cancer Growth and Induces Apoptosis via p53/mTOR Signaling Pathway.

The Striga angustifolia (D. Don) C.J. Saldanha was used as an Ayurvedic and homeopathic medicine for cancer by the tribal peoples of the Maruthamalai Hills, Coimbatore, India. Hence, the traditional use that has been proven to be effective lacks convincing scientific references. This present study was conducted to investigate the presence of potentially bioactive compounds from S. angustifolia and provides a scientific basis for the ethnobotanical utility. The organosulfur compound 5,5'-dithiobis(1-phenyl-1H-tetrazole) (COMP1) was isolated from S. angustifolia extracts, and the structures of COMP1 were elucidated and characterized by using C and H nuclear magnetic resonance (NMR) and single crystal X-ray powder diffraction (XRD). Our findings showed that COMP1 significantly reduced cell proliferation of breast and lung cancer cells, but not that of non-malignant epithelial cells. Further analysis revealed that COMP1 promoted cell cycle arrest and apoptosis of lung cancer cells. Mechanistically, COMP1 facilitates p53 activity and inhibits mammalian target of rapamycin (mTOR) signaling, thereby inducing cell cycle arrest and apoptosis of lung cancer cells by inhibiting cell growth. Our findings suggest that COMP1 may serve as a potential drug for lung cancer through the regulation of p53/mTOR pathways.