Methods: The methanol crude extracts (MBD and MPD) were prepared from the raw material of porcupine dates. The tannin-rich fractions (BDTF and PDTF) were isolated from their methanol crude extracts using column chromatography. The presence of tannins in BDTF and PDTF extracts was determined by fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses. The cytotoxicity and anti-DENV-2 activities including virus yield inhibition, virucidal, virus attachment and pre-treatment assays of the extracts were examined in Vero cells.
Results: Our findings revealed that all the extracts of porcupine dates exhibited antiviral activity against DENV-2 in Vero cells. The IC50 of BDTF and PDTF were 25 µg/mL and 11 µg/mL respectively, while their methanol crude extracts demonstrated lower antiviral efficacy (IC50 ≈ 101-107 µg/mL). BDTF and PDTF also exerted a similar higher virucidal effect (IC50 of 11 µg/mL) than methanol crude extracts (IC50 ≈ 52-66 µg/mL). Furthermore, all the extracts inhibited the attachment of DENV-2 by at least 80%. Pre-treatments of cells with BDTF and PDTF markedly prevented DENV-2 infection when compared to methanol crude extracts.
Conclusion: This study suggests that porcupine dates possess antiviral properties against DENV-2, which is attributed to its tannin compounds.
METHODS AND RESULTS: The crude extracts of E. pubescens were obtained through methanol extraction, and evaluated for antimicrobial activities. From this extract, 1,7-bis(3,4-dihydroxyphenyl)heptan-3-yl acetate (etlingerin) was isolated. When compared to curcumin (a compound with a similar chemical structure), etlingerin showed twofold lower minimum inhibitory concentration values while also being bactericidal. Through time kill assay, etlingerin showed rapid killing effects (as fast as 60 min) against the Gram-positive bacteria (Staphylococcus aureus ATCC 43300 and Bacillus subtilis ATCC 8188). Further assessment revealed that etlingerin caused leakage of intracellular materials, therefore suggesting alteration in membrane permeability as its antimicrobial mechanism. Cytotoxicity study demonstrated that etlingerin exhibited approximately 5- to 12-fold higher IC50 values against several cell lines, as compared to curcumin.
CONCLUSIONS: Etlingerin isolated from E. pubescens showed better antibacterial and cytotoxic activities when compared to curcumin. Etlingerin could be safe for human use, though further cytotoxicity study using animal models is needed.
SIGNIFICANCE AND IMPACT OF THE STUDY: Etlingerin has a potential to be used in treating bacterial infections due to its good antimicrobial activity, while having potentially low cytotoxicity.
METHODS: Gallic acid (1), and methyl gallate (2), were isolated via bioassay-directed isolation, and they exhibited anticancer properties towards several cancer cell lines, examined using MTT cell viability assay. Pyrogallol (3) was examined against the same cancer cell lines to deduce the bioactive functional group of the phenolic compounds.
RESULTS: The results showed that the phenolic compounds could exhibit moderate to weak cytotoxicity towards certain cell lines (GI50 30 - 86 µM), but were inactive towards DU145 prostate cancer cell (GI50 > 100 µM).
CONCLUSION: It was observed that pyrogallol moiety was one of the essential functional structures of the phenolic compounds in exhibiting anticancer activity. Also, the carboxyl group of compound 1 was also important in anticancer activity. Examination of the PC-3 cells treated with compound 1 using fluorescence microscopy showed that PC-3 cells were killed by apoptosis.