Phytobiological Investigation and In Silico Docking Study of Secondary Metabolites from Saussurea lappa Roots

Chromatographic exploration of methanol extract derived from Saussurea lappa roots yielded four sesquiterpene lactones, santamarin (1), dehydrocostuslactone (2), costunolide (3) and zaluzanin C (4) along with the well-known triterpene, beta-sitosterol (5). Chemical structures were determined based on extensive 1D/2D NMR analyses. In antiviral assay, compounds 1-5 showed % antiviral activity ranging from 2.18 +/- 3.1 to 53.7 +/- 10.05 % and from 15.39 +/- 4.83 to 92.91 +/- 2.47 % when tested against hepatitis A virus (HAV) and Herpes simplex virus type 1 (HSV-1), respectively. Molecular docking simulation studies against (HSV-1) DNA polymerase and (HAV) 3 C proteinase enzymes showed similar binding interactions as for acyclovir. Compounds (1 and 3-5) showed moderate to potent antibacterial activity against Bacillus subtilis ATCC 6633 (MIC values between 7.9 and 31.25 mu g/ml) whereas, dehydrocostuslactone (2) and costunolide (3) exhibited comparable antibacterial activities against Pseudomonas aeruginosa ATCC 90274 (MIC values=125 mu g/ml) compared to gentamicin as a positive control. In cytotoxicity assay against human colorectal carcinoma (HCT-116) and human epithelioid cervical carcinoma (HeLa), compounds 1 and 4 exhibited weak to moderate activities. Compound 1 showed IC50 values of 46.05 mu g/ml (185.44 mu M) and 59.38 mu g/ml (239.1153 mu M) whereas compound 4 showed IC50 values of 36.08 mu g/ml (146.48 mu M) and 46.59 mu g/ml (189.175 mu M), respectively.