final bipin khanal.docxANTIOXIDANT, ANTIBACTERIAL AND HR-LCMS ANALYSIS OF SECONDARY METABOLITES PRES
Date
2025-02-06
Journal Title
Journal ISSN
Volume Title
Publisher
Department of Chemistry, Birendra Multiple Campus
Abstract
Antioxidant, antibacterial properties and secondary metabolites present in Psidium guajava
L. (Guava) fresh leaves are still to explore fully. This study aimed to evaluate the
phytochemical constituents present in fresh Psidium guajava L. (Guava) leaves to validate
their medicinal potential.
The samples were collected (GPS point 27˚68'33" N 84˚43'33" E) from Bharatpur
Metropolitan City-11, Chitwan, Nepal. Spectrophotometric methods were used to
determine the phenolic, flavonoid, and tannin contents as well as the phosphomolybdenum
and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assays. The Folin-
Ciocalteu method was used to quantify the phenolic content, aluminium chloride
colorimetric method was used to measure the flavonoid content and Folin-Ciocalteu
method was used to calculate the tannin content. Antioxidant activity was assessed using
the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay and the
phosphomolybdenum assay. Antibacterial activity was determined using the agar diffusion
method and extract was characterised using HR-LCMS.
The qualitative analysis revealed the presence of terpenoids, glycosides, polyphenols,
alkaloids, flavonoids and tannins. However, for quantitative evaluation maceration showed
higher concentrations of total phenolic content (316.1±7.4 mg gallic acid equivalent
(GAE)/g), total flavonoid content (257.9±4.4 mg/g quercetin equivalent (QE)),
phosphomolybdenum assay (125.0±2.1mg ascorbic acid equivalent (AAE)/g), and DPPH
free radical scavenging capacity (IC50=6.08 μg/mL). Soxhlet extract showed highest tannin
content consisting of 563.6±4.5μg/mL. The antimicrobial assay showed good activity
against five bacterial strains. A total of 144 different metabolites were observed in HRLCMS
out of which 104 were known compounds and other 40 compounds were
unidentified compounds. Among them four compounds were reported for the first time in
Psidium guajava L. (Guava) fresh leaves.
Among the extraction methods used, maceration was the most effective for phenolic,
flavonoid and antioxidant contents whereas sonication was the least effective. Furthermore,
the secondary metabolites observed in HR-LCMS analyses possess significant impact on
the antioxidant, phenolic, flavonoid, alkaloid, tannin, and antimicrobial properties. These
results offer scientific support for the traditional use of fresh Psidium guajava L. leaves for
medicinal purposes.
Keywords: Alkaloid, Flavonoid, Phytochemicals, Phenolic, Tannin.