| dc.description.abstract | The aim of this study is to investigate the effect of dried method as well as leaf maturity
which influences factors of total phenolic and flavonoid contents yielded, antioxidant
and antimicrobial activity of guava leaf extracts. A colorimetric assay, 2,2-diphenyl 1-picrylhydrazyl (DPPH) free radical scavenging assay, minimum inhibitory
concentration (MIC) and disc diffusion methods were used to evaluate the potent of
extracts in terms of total phenolic contents (TPC) and flavonoid contents (TFC),
antioxidant activities, and antimicrobial activities, respectively. The study of
extraction conditions showed that dry leaves were dominant rather than fresh leaves,
additionally, in terms of leaf ages, dry young samples yielded the highest activity
among others, regarding TPC, TFC, antioxidant capacities. This indicated that the
effects of pretreatments including method extraction and leaf maturity greatly
influenced the activities of leaves. Particularly, for total phenolic and flavonoid
contents, the young leaf extracts yielded the higher values rather than that of old leaf
extracts, which were 1517.22 ± 41.94 (mg GAE/g LE) and 1066.67 ± 115.47 (mg QE/g
LE), respectively. The young guava leaves of hot water extraction exhibited the potent
antioxidant power while comparing to that of commercial vitamin C of 294.58 ± 1.46
and 112.10 ± 0.48 (µg/mL), respectively. However, the extracts of guava leaves in
both leaf age categories showed no inhibition against Staphylococcus aureus,
Escherichia coli and Pseudomonas aeruginosa. Furthermore, guava leaf extracts in the
face serum product also demonstrated its high antioxidant potential of 79.69 ± 0.70
(%) against commercial Bio-essence antioxidant lotion, which was 24.32 ± 3.96 (%). | en_US |
