Drimane Sesquiterpene-Rich Volatile Oil Profile of Water Pepper (Persicaria hydropiper), a Widely Distributed Spicy Herb.

Water pepper (Persicaria hydropiper) is a globally distributed annual herb, used as a peppery food flavor in Asian countries. Ambiguous botanical identification, unvalidated chemical analysis, and a lack of in-depth studies have made its volatile flavor profile elusive. This study established the essential oil profile of a taxonomically authenticated water pepper sample through integrative spectroscopic and spectrometric techniques. It was exclusively rich in sesquiterpenes, particularly drimane-type sesquiterpenoids. In total, eighteen sesquiterpenes were characterized unambiguously, among which six were identified for the first time in this oil. These metabolites were quantified in a regional library of 26 water pepper samples from northeast India to evaluate its chemical consistency and richness. Three drimane sesquiterpenes, namely drimenol (64.9-154.6 mg/g oil), euryfuran (9.4-78.5 mg/g), and isodrimeninol (34.7-112.1 mg/g), were consistently most abundant across samples. The feasibility of their preparative purification was also demonstrated, achieving yields of 17.5%, 8.5%, and 6.1% w/w, respectively. The quantity of 11-nordrim-8-en-12-al, humulene-1,2-epoxide, β-caryophyllene oxide, and isopolygodial/polygodial was moderately high. Polygodial, the pungent principle of water pepper and major constituent of the solvent extract, was relatively low-abundant in the essential oil. Drimenol was found to be a cytotoxic candidate against cervical and lung cancer cell lines with an IC of 14.75 and 7.64 µM, respectively. The current study deciphered key information on the volatile flavor profile of water pepper. A wide distribution, weedy, herbal nature, high metabolite yield, and the feasibility of preparative-scale isolation make this herb a 'sustainable' source of three drimane sesquiterpenes.