Antioxidant activity of unpolished Riceberry rice (Oryza sativa) and the inhibition of calcium oxalate crystal growth and aggregation

Abstract

Background : The inhibition of calcium oxalate monohydrate (COM) growth and aggregation can prevent the kidney stone formation. Black-purple rice (Oryza sativa), including Riceberry rice, contains high amount of antioxidant substances, such as anthocyanin, gamma - oryzanol and alpha-tocophorol. A previous study revealed that the high antioxidant content substances can prevent the formation of CaOx crystal.

Objective : To prove the high antioxidant activity of unpolished Riceberry rice extract can inhibit the growth and aggregation of CaOx crystal, especially COM.

Methods : Unpolished Riceberry rice (UBR) grain was extracted by ethanol. The monomeric anthocyanin content of the extract was assessed by pH differential method. The total phenolic compound was determined by Follin Ciocalteu reagent assay. The antioxidant activity assays were carried out by 1,1 diphenyl-2-picryl-hydrazyl radical scavenging activity assay and ferric reducing antioxidant power assay. The extracts were then incubated with the CaOx crystal, the number and the aggregation of CaOx crystal were then counted.

Results : The results revealed that UBR extract contained high amount of anthocyanin content and possessed antioxidant activities. The co-incubation of the extracts and CaOx crystal could inhibit the growth of COM with dose-dependent pattern. Moreover, the aggregation of the CaOx crystal was significant reduced in the incubation with higher concentration of UBR extract.

Conclusion : This study indicated that UBR extract performed antioxidant activity, and could inhibit calcium oxalate crystal growth and aggregation. These results showed the high therapeutic potential of the UBR extract on the formation of kidney stone.