The responses of the cotton plant, Gossypium hirsutum L. to herbivory by Spodoptera litura F. was studied in various laboratory experiments as a measure to understand the defense strategies of certain plant metabolites. Insect feeding damage enhanced the concentration of total phenol content and proteins, whereas amount of carbohydrates and amino acids were reduced. The experiments on estimation of anti-oxidative enzymes revealed stimulation in peroxidase, catalase, and superoxide dismutase levels and reduction in polyphenol oxidase and phenylanine ammonia lyase levels, signifying their defensive role in the plant. Specific phenolic acid changes were further carried out using High Performance Liquid Chromatography (HPLC), and distinct elevations in the gallic acid, catechin, and caffeic acid levels were observed in the infested cotton plant. Feeding assays towards S. litura with these phenolic compounds revealed activated detoxifying enzymes including ${eta}$-glucosidase, carboxyl esterase, and glutathione-S-transferase in the insect gut indicating the toxicity. The aim of present study is to aid in further use of these specific phenolic acids towards effective management of the cotton pest, S. litura.