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

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 IC₅₀ 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.