Fractionation based evaluation of phytochemical constituents, antimicrobial and allelopathic potential of Piper chaba, Hunter. stem and identification of "Pipercyclobutanamide-A" as a strong allelopathic agent

Piper chaba, Hunter. is a less known medicinal spice. Its medicinal properties have been studied thoroughly but its role as a source of agrochemicals has not been studied yet. So, in the present work, we are interested to explore its other biological activities. Fractionated quantitative biochemical analysis revealed that all fractions contained substantial amounts of phenolics (ranging from 863.75 mg to 1073.11 mg GAE/g of dry extract), flavonoids (164.01 mg to 244.57 mg QE/g of dry weight) and tannins (42.86 mg to 64.88 mg TAE/g dry extract) except acetone fraction. All fractions of P. chaba revealed strong fungicidal activity with Inhibition Zone Diameter [IZD] ranging from 32.49 to 36.66 mm except acetone fraction. In case of bactericidal activity, all the fractions except hexane fraction exhibited strong effect with IZD ranges from 14.96 to 30.39 mm against all the tested species. Dose dependent bioassay experiment on rice showed that methanol fraction of P. chaba possesses strong allelopathic activity with IC50 value 202.77 mu g/mL for root length and 509.1 mu g/mL for shoot length. As methanol fraction of P. chaba exhibited strong allelopathic activity, we were interested to identify the actual compound responsible for that activity. LCMS analysis of purified methanol fraction of P. chaba revealed the presence of "Pipercyclobutanamide-A" as a major compound- and this is the first report of this compound from stem of P. chaba. Therefore, methanol fraction of Piper chaba could be used as natural source of compounds with agrochemical and antimicrobial potential for sustainable agriculture and pharmaceutical purposes.