Gossypium hirsutum L. and Gossypium barbadense L.: differences in phytochemical contents, antioxidant and antimicrobial properties.

Abstract

Gossypium L. generally called cotton plants are used indiscriminately in traditional medicine without cognisance to the fact that there are different cotton species and the likelihood of differences in phytochemical content and ultimately, their medicinal capabilities. This study reports the differences in the phytochemical contents, antioxidant and antimicrobial properties of extracts of leaves of two cotton species, Gossypium hirsutum L. and Gossypium barbadense L. Leaf samples from mature G. hirsutum and G. barbadense plants were collected, shadedried and powdered. Phytochemical contents were quantified while antioxidant activity was tested through 1,1- diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and reducing power. Aqueous, decocted aqueous and ethanol leaf extracts of G. hirsutum and G. barbadense were tested against Esherichia coli (known to cause gastrointestinal infections and urinary tract infections), Staphylococcus aureus (known to cause skin infection), Klebsiella pneumoniea and Pseudomonas aeruginosa (known to cause bronchial infections and pneumonia). The results showed that tannins and phenols were present in leaves of G. hirsutum but absent in G. barbadense. Leaves of G. hirsutum contained significantly higher (at p<0.05) amount of total glycosides (156.44 ± 2.05 mg /100g) and flavonoid (120.85 ± 0.32 mg /100g, twice as much) than G. barbadense. Gossypium hirsutum showed higher DPPH free radical scavenging activity and reducing power than G. barbadense. Gossypium hirsutum showed higher zones of inhibition (mm) in all organisms than G. barbadense. It can therefore be concluded that G. hirsutum leaves have higher phytochemical contents as well as antioxidant and antimicrobial activities than G. barbadense. Gossypium hirsutum is therefore recommended for use as against G. barbadense where the choice is available.

Keywords: Antimicrobial, Antioxidant, 1,1-diphenyl-2-picrylhydrazyl (DPPH), Gossypium hirsutum, Gossypium barbadense, Phytochemical