Anthocyanins in Red Jasmine Rice (Oryza sativa L.) Extracts and Efficacy on Inhibition of Herpes Simplex Virus, Free Radicals and Cancer Cell

Abstract

Rice is one of the most important food crops in many countries, with nutritional value and health benefits. In this study, the ethanolic and aqueous extracts of red jasmine rice from Chiang Mai, Thailand were examined for their anthocyanins and phenolic contents. The antioxidant and antiviral activity against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), as well as anticancer activity, were investigated. The total anthocyanins content of 708.03 ± 11.56 mg Cy-3-glc equivalent/g extract, determined from the ethanolic extract, was higher than the aqueous extract. However, the aqueous extract showed the highest total phenolic compound of 81.91 ± 0.51 mg GAE/g extract. In addition, the ethanolic extract demonstrated higher antioxidant activity than aqueous extract using DPPH, ABTS, and FRAP assays by 28.91 ± 3.26 mg GAE/g extract, 189.45 ± 11.58 mg 24 TEAC/g extract, and 3292.46 ± 259.64 g FeSO₄/g extract, respectively. In the antiviral assay, it was found that the ethanolic extract of red jasmine rice could inhibit HSV-1 more effectively than HSV-2 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. The extract also demonstrated the highest reduction of HSV-1 particles at 4 h after treatment and the inhibition of HSV-1 replication. The ethanolic extract exhibited a higher toxicity level than the aqueous extract, as well as the potential to induce DNA fragmentation by intrinsic and extrinsic apoptosis pathways on the Caco-2 cells. These findings suggest that red jasmine rice extract demonstrates nutritional value and biological activity on HSV, free radicals, and cancer cell inhibition.

Keywords: anthocyanins; anticancer; antioxidant activity; antiviral activity; herpes simplex virus; red jasmine rice.

Figure 1

Inhibitory effect of aqueous red jasmine rice extract at 1250 µg/mL and ethanolic extract at 625 µg/mL on HSV-1 and HSV-2 before, during, and after viral attachment. (*** indicated, p < 0.0001).

Figure 2

Log titers of HSV-1 (a) and HSV-2 (b) at 0, 6, 12, 24, 30, and 36 h after treatment with ethanolic extract of red jasmine rice at 625 µg/mL, compared with antiviral agent, acyclovir and virus control.

Figure 3

Log titers of HSV-1 (a) and HSV-2 (b) titer at 0, 1, 2, 3, and 4 h after treatment with the extracts from ethanolic and aqueous extracts of red jasmine rice, compared to viral control.

Figure 4

Effect of the ethanolic and aqueous extracts of red jasmine rice on Caco-2 cell viability. The cells were treated with various concentrations of 39.06 to 5000 µg/mL for 48 h and toxicities of the cells after treatment were investigated by MTT assay.

Figure 5

Morphological characteristics of apoptosis were detected in the cells after treatment with 250 µg/mL of red jasmine rice ethanolic extract and 3000 µg/mL of red jasmine rice aqueous extract for 48 h, when compared to untreated cells.

Figure 6

DNA fragmentation in treated Caco-2 cells after 48 h of treatment with 250 µg/mL of red jasmine rice ethanolic extract and 3000 µg/mL of red jasmine rice aqueous extract after investigation by TUNEL assay and fluorescent microscope.

Figure 7

The qRT-PCR analysis of apoptosis-related gene after 3 h of treatment of Caco-2 cell with red jasmine rice ethanolic extract (a) and aqueous extract (b), compared with untreated cell control. Data are expressed as mean ± SD (n = 3 independent assays). (*** indicated, p < 0.0001).