Phytochemical profiling and cellular antioxidant efficacy of different rice varieties in colorectal adenocarcinoma cells exposed to oxidative stress

Abstract

In the present study, white (Baegilmi), brown (hyunmi) and black (chalheugmi) Korean local rice varieties ethanol extracts were analyzed for in-vitro antioxidant assays (ABTS, FRAP and DPPH), cellular antioxidant activities (CAAs) and phenolic phytochemicals content. The highest antioxidant assays, phenolic, flavonoid and anthocyanins content were identified among the free fractions of black rice. Phenolic phytochemicals were detected and quantified using the ultra-high-performance liquid tandem chromatography quadrupole flight mass spectrometry (UHPLC-Q-TOF-MS2). Which indicated the richness of several phytochemicals like ascorbic acid, vanillic acid, p-coumaric acid, catechin, epigallocatechin and quercetin in black rice than in other rice samples. The cellular antioxidant activities (CAA) of black rice were found equivalent to that of ascorbic acid, the standard employed in the assay. The CAAs of free fractions were as follows: white rice < brown rice < black rice. These findings are significant for enhancing human health through increased consumption of black and brown rice in the development of functional food products.

Fig 1. Ethanol extracts from rice cultivars have antioxidant properties.

DPPH radical scavenging IC₅₀ values, ABTS radical scavenging IC₅₀ values, and FRAP radical scavenging IC₅₀ values. A minimum of three analyses were carried out. Significant differences are indicated by different lower case letters (p < 0.05).

Fig 2

(A) CAA graph of rice extracts at 1 mg/mL. (B) Rice extracts at 0.5–5 mg/mL inhibited peroxyl radical-induced DCFH oxidation to DCF and ROS production in Caco-2 cells. Using one-way ANOVA, the data were reported as means ± standard deviations (n = 3). Tukey’s test at p < 0.05 shows significant differences between the columns using different alphabets (a–d). Note: (DCFH: 2’,7’–dichlorofluorescein diacetate, DCF: 2’, 7’–dichlorofluorescein, ROS: Reactive oxygen species, CAA- Cell antioxidant assay).

Fig 3. Heat map showing levels of phytochemicals in different pigmented and non-pigmented rice (white, brown, and black) extracts.

Fig 4. Principal component analysis (PCA) of rice samples (white, brown & black) was shown by comparing PC 1(component 1) with PC2 (component 2).