Biological properties of pigmented rice and bean extracts for suppression of herpes simplex viruses and colon cancer cells

Abstract

Rice is one of the most important food crops in many countries, with nutritional value and health benefits while bean is a major grain consumed worldwide. Therefore, the natural active substances. from pigmented rice and bean extracts become of considerable interest to study antioxidant activities, an efficacy inhibition herpes simplex virus and antiproliferation of colon cancer cell. Six samples of organic rice and bean were investigated in this research. These samples were extracted with distilled water and 95% ethanol. The highest percentage yield was observed from the black bean aqueous extract. Then, the extracts were examined for antioxidant activity using DPPH and ABTS assays. The result revealed that the aqueous extract of black glutinous rice showed the highest antioxidant activity using DPPH assay by 31.58 ± 0.03 mg of gallic acid/g extract. Whereas, the ethanolic extract of red jasmine rice had the highest antioxidant activity of 189.45 ± 11.58 mg TEAC/g extract by the ABTS method. In addition, the total anthocyanins content of 3,188.37 ± 40.81 mg Cy-3-glc/g extract was determined from the ethanolic extract of black glutinous rice. In addition, the ethanolic extract of red jasmine rice showed the highest total phenolic compound of 81.91 ± 0.51 mg of gallic acid/g of extract. Anti-HSV activity of pigmented rice and bean extracts were examined for cytotoxicity on Vero cell by MTT assay. The result revealed that the ethanolic of soy bean showed the lowest cytotoxicity with CD50 value more than 5,000 µg/ml, while the red jasmine rice ethanolic extract revealed the highest cytotoxicity in Vero cells with CD50 value of 862.05 ± 28.14 µg/ml. After that, nontoxic concentrations of pigmented rice and bean extracts were used to examine against HSV-1 and HSV-2 by plaque reduction assay. It was found that the ethanolic extract of red jasmine rice completely inhibited HSV-1 when treated before, during, and after the viral attachment on Vero cells, with 50% effective doses of 227.53 ± 2.41, 189.59 ± 7.76, and 192.62 ± 2.40 µg/ml, respectively. Moreover, the aqueous extract of red bean exhibited the highest inhibition on HSV-2 when treated before and during viral attachment stage, with 50% effective doses of 1,797. 69 ± 7.89 and 1,447.82 ± 78.34 µg/ml, respectively. Thus, the study of anti-viral effect on various stages of HSV infection was performed. Direct inactivation kinetic of HSV particles revealed the high ability of the ethanolic extract of red jasmine rice on inactivation of HSV-1 particles with the log reduction of viral titer by 2.40 ± 0.30 PFU/ml, while the aqueous extract of red bean showed the highest anti-HSV-2 activity with log reduction of viral titer by 1.34 ± 0.33 PFU/ml at 4 h after treatment. Furthermore, it was found that the ethanolic extract of red jasmine rice affected viral replication and showed the highest inhibition of HSV-1 replication. Whereas, the aqueous extract of red bean on HSV-2 replication demonstrated the most inhibitory activity at 36 h post infection. Moreover, cytotoxicity of extracts on Caco-2 cells was determined by MTT assay. The ethanolic extract of red jasmine rice showed the highest toxicity on Caco-2 cells with IC50 value of 372.56 ± 15.54 µg/ml. The ethanolic extract of red jasmine rice exhibited a higher toxicity level than the aqueous extract of red jasmine rice and the potential to induce the DNA fragmentation by intrinsic and extrinsic apoptotic pathways on the Caco-2 cells. Moreover, the DNA fragmentation was also induced by the ethanolic extract of black bean through the intrinsic apoptotic pathway by activity of caspase 9 enzyme. Therefore, the knowledge obtained from this study may be useful for development of effective antioxidant, anti-HSVs and anticancer agents from pigmented rice and bean extracts in the future.