Antioxidant and antimicrobial activities of pink guava leaves and seeds

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W.Z. Wan Nur Zahidah, A. Noriham and M.N. Zainon

Abstract

The antioxidant and antimicrobial activities of leaves and seeds of pink guava (Psidium guajava L.) were investigated. They were analyzed for total phenolic content (TPC), total flavonoid content (TFC), scavenging of 2,2-diphenyl-1- picrylhydrazyl radical (DPPH) and ferric reducing antioxidant power (FRAP) assays, and oxidative stability of fats using Rancimat test. The antimicrobial activity was determined using disc diffusion method against the bacteria Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Pseudomonas aeruginosa as well as the fungi Aspergillus niger and Candida albicans. Results showed that pink guava leaves possessed a higher TPC (368.61 ± 25.85 mg/100 g GAE) compared to the seeds (79.03 ± 3.48 mg/100 g GAE). The total flavonoid content showed the same trend where the leaves showed higher value than the seeds extract. The leaves exhibited high scavenging effect (90%) as determined by DPPH while the seeds had 36% scavenging effect. The FRAP values of guava leaves were also higher than guava seeds extract. Using the Rancimat test, all natural and synthetic antioxidants significantly delayed the development of oxidative destruction in margarine. Guava leaves extract also exhibited antimicrobial effect by inhibiting the growth of Bacillus subtilis and Staphylococcus aureus. Pink guava leaf extract has the potential to be used as a functional food ingredient or as a bioactive ingredient in the food and pharmaceutical industry.

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