Antioxidant and antimicrobial activities and starch digestion rate of the organically- and non-organically grown traditional rice varieties in Sri Lanka

Abstract

Abstract:The study was designed to assess the total phenolic content (TPC), free radical scavenging activity, antimicrobial property and in vitro starch digestion rate of three traditional rice varieties grown organically and non-organically in Sri Lanka. The 70% ethanol extractions of rice were subjected to TPC, DPPH -free radical scavenging assays to determine antioxidant activity, and antimicrobial susceptible test against three bacteria, namely, Escherichia coli, Salmonella typhi and Staphylococcus aureus to determine antimicrobial properties. Starch digestion of cooked rice samples were evaluated under in vitro conditions. Both TPC and free radical scavenging activity was significantly higher (P<0.05) in organically produced traditional rice while the non-organically produced traditional rice samples showed a significantly higher (P<0.05) antimicrobial activity against S. typhi and S. aureus. There was no significant difference (P>0.05) in the in vitro starch digestion rate between the two groups. Though the study only considered traditional rice varieties, the results suggested that organically produced traditional rice samples performed better than those non-organically produced, with regard to the antioxidant properties such as TPC and free radical scavenging activity. The Madathawalu cultivar performed superior role in total phenolic content, free radical scavenging activity and Glycemic Index compared to that of two other traditional rice varieties, namely, Suwandel and Handiran.

Narrative Review on Nutritional Composition, Antioxidant Activity and Health Benefits of Sri Lankan Traditional Rice Varieties

“…However, these values were significantly higher for non-organically produced Madathawalu seeds which showed 3.83±0.3 for Salmonella typhi and 5.73±0.2 for Staphylococcus aureus. However, both organically and nonorganically produced Madathawalu seed samples had not shown an anti-microbial effect on Escherichia coli [25].…”

“…Further, they found that organically grown Madathawalu has a high total phenolic content (2.22±0.03 mg gallic acid equivalent/g of rice extract) also compared to the non-organically produced sample (1.42±0.01 mg ascorbic acid equivalent/g of rice extract). The red pericarp rice varieties used in their study (Madathawalu and Handiran) showed higher antioxidant values than the tested white pericarp variety which is Suwandel [25].…”

“…In 2017, Hemanthi and her co-workers [25] showed that organically grown Madathawalu seed samples has high antioxidant activity on DPPH assay (16.89±0.78 mg ascorbic acid equivalent/ g of rice extract) to respective non-organically produced seed samples (9.40±0.25 mg ascorbic acid equivalent/g of rice extract). Further, they found that organically grown Madathawalu has a high total phenolic content (2.22±0.03 mg gallic acid equivalent/g of rice extract) also compared to the non-organically produced sample (1.42±0.01 mg ascorbic acid equivalent/g of rice extract).…”

“…The scientific data on the anti-bacterial activity of rice varieties also helps to assess the health benefits of traditional varieties since rice has emerged as an intriguing source of natural antibacterial agent [26]. According to Hemanthi et al [25], organically grown Madathawalu seed samples have shown zone inhibition in the antimicrobial susceptibility test, which were done for Salmonella typhi (3.4±0.3) and Staphylococcus aureus (5.34±0.3). However, these values were significantly higher for non-organically produced Madathawalu seeds which showed 3.83±0.3 for Salmonella typhi and 5.73±0.2 for Staphylococcus aureus.…”