Quality assessment and antimicrobial activities of psidium guajava leaves

Abstract

Khee Nok cultivar is the indigenous variety of P.guajava L. (Myrtaceae) in Thailand. Its leaves were collected from 15 places throughout Thailand and investigated for the pharmacognostic specification of leaves and chemical constituents of the leaf essential oil. The results demonstrated the contents of loss on drying, total ash, acid insoluble ash, ethanol-soluble extractive value, water-soluble extractive value, moisture and volatile oil content as 7.88±0.50, 7.03±0.31, 1.42±0.25, 8.61±0.78, 10.21±0.52, 8.71±0.47 and 1.54±0.17 by dried weight, respectively. Anatomical and histological structures of the leaf were illustrated. Unicellular trichomes and oil glands were abundant. Trichomes were found in both dorsal and ventral region. The average trichome numbers in 1 mm2 of dorsal and ventral area were 24.21±3.75 and 46.20±4.68 respectively. The average oil gland numbers in 1 mm2 was count in the same way and revealed the average of 38.94±3.96. Thin layer chromatographic fingerprint of ethanolic extract was achieved using dichloromethane: ethyl acetate: methanol: acetic acid 8:4:2:0.1 as mobile phase and visualization under day light, UV 254 nm, 365 nm and staining with sulfuric acid reagent. The leaf essential oil was extracted by hydrodistillation. At least 40 chemical constituents of the essential oil were identified by GC/MS. The major constituents were caryophyllene (28.21±2.91%), limonene (7.17±5.47%), copaene<alpha-> (8.06±3.58%), aromadendrene (6.86±3.86%) and globulol (5.90±2.89%). The essential oil was investigated for antimicrobial activity by agar diffusion assay and demonstrated bactericidal activity against Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis and Micrococcus luteus.