ABSTRACT
Halymenia durvillei is a red alga that is commonly utilized in the Philippines as food and as a source of high-value natural products for industrial applications. However, there are no studies regarding the microbial community associated with H. durvillei and its potential applications. This study aimed to isolate and identify the epiphytic bacteria of H. durvillei and determine their antimicrobial and quorum sensing inhibitory (QSI) effects. The thalli of H. durvillei were collected at the shores of Santa Fe, Bantayan, Cebu, Philippines. Bacterial isolates were identified using 16S rRNA, and their ethyl acetate (EtOAc) extracts were subjected to antimicrobial susceptibility tests against representative species of yeast and Gram-negative and Gram-positive bacteria. Their QSI activity against Chromobacterium violaceum was also determined. Fourteen distinct bacterial colonies belonging to four genera, namely Alteromonas (3), Bacillus (5), Oceanobacillus (1) and Vibrio (5), were successfully isolated and identified. All 14 bacterial isolates exhibited antibacterial effects. EPB9, identified as Bacillus safensis , consistently showed the strongest inhibition against Escherichia coli , Staphylococcus aureus and Staphylococcus epidermidis , with minimum inhibitory concentrations (MICs) ranging from 0.0625 to 1.0 mg ml-1. In contrast, all 14 isolates showed weak antifungal effects. Both B. safensis (EPB9) and Bacillus australimaris (EPB15) exhibited QSI effects at 100 mg ml-1, showing opaque zones of 3.1±0.9 and 3.8±0.4 mm, respectively. This study is the first to isolate and identify the distinct microbial epiphytic bacterial community of H. durvillei and its potential as an abundant resource for new antibacterial and QSI bioactives.
ABSTRACT
Whereas Korean ginseng, Panax ginseng Meyer, is harvested in the fall, the variation of ginsenoside content in field-grown ginseng across seasonal development has never been investigated in Korea. Thus, ultra-high performance liquid chromatography (UHPLC) analysis of nine major ginsenosides, including ginsenoside Rg1, Re, Rf, Rg2, Rb1, Rc, Rb2, Rd, and Ro, in the roots of five-year-old P. ginseng cultivated in Bongwha, Korea in 2017 was performed. The total ginsenoside content changed as many as three times throughout the year, ranging from 1.37 ± 0.02 (dry wt %) in January to 4.26 ± 0.03% in May. Total ginsenoside content in the harvest season was 2.49 ± 0.03%. Seasonal variations of panaxadiol-type ginsenosides (PPD) and panaxatriol-type ginsenosides (PPT) were found to be similar, but more PPD was always measured. However, the seasonal variation of oleanolic acid-type ginsenoside, Ro, was different from that of PPD and PPT, and the highest Ro content was observed in May. The ratio of PPD/PPT, as well as other representative ginsenosides, was compared throughout the year. Moreover, the percent composition of certain ginsenosides in both PPD and PPT types was found to be in a complementary relationship each other, which possibly reflected the biosynthetic pathway of the related ginsenosides. This finding would not only provide scientific support for the production and quality control of the value-added ginseng products, but also facilitate the elucidation of the ginsenoside biosynthetic pathway.
