The processed drinks produced from grass of three varieties of rice (Jasmine, Sukhothai 1 and Sukhothai 2) and one each from wheat and barley grasses were analyzed for chlorophyll and total phenolic contents, and antioxidant activities [ABTS radical cation decolorisation assay and ferric reducing/antioxidative power (FRAP) assay]. The consumer acceptance of all the drinks was also evaluated. One serving size (200 mL) of these contained 82-958 μg of chlorophyll, 5.60-26.14 mg Gallic acid equivalent for total phenolic content and their antioxidant activities, ABTS and FRAP values were 17.88-35.18 mg Vitamin C equivalent and 5.66-23.70 mg FeSO equivalent, respectively. The overall consumer acceptability of drinks was significantly correlated to their aroma intensity and consumer preference on aroma and flavor. Jasmine and Sukhothai 1 rice grass drinks were most preferred, however, one subgroup preferred grass drink from Sukhothai 1 rice, while the second subgroup preferred the drinks from Sukhothai 2 rice and Jasmine rice. Wheat and barley grass drinks were not preferred by both subgroups.

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Rice grass has been reported to contain bioactive compounds that possess antioxidant and free-radical scavenging activities. We aimed to assess rice grass extract (RGE) drink by determining catechin content, free-radical scavenging and iron-binding properties, as well as toxicity in cells and animals. Young rice grass (Sukhothai-1 strain) was dried, extracted with hot water and lyophilized in a vacuum chamber. The resulting extract was reconstituted with deionized water (260 mg/40 mL) and served as Sukhothai-1 rice grass extract drink (ST1-RGE). HPLC results revealed at least eight phenolic compounds, for which the major catechins were catechin, epicatechin and epigallocatechin-3-gallate (EGCG) (2.71–3.57, 0.98–1.85 and 25.47–27.55 mg/40 mL serving, respectively). Elements (As, Cu, Pb, Sn and Zn) and aflatoxin (B1, B2, G1 and G2) contents did not exceed the relevant limits when compared with WHO guideline values. Importantly, ST1-RGE drink exerted radical-scavenging, iron-chelating and anti-lipid peroxidation properties in aqueous and biological environments in a concentration-dependent manner. The drink was not toxic to cells and animals. Thus, Sukhothai-1 rice grass product is an edible drink that is rich in catechins, particularly EGCG, and exhibited antioxidant, free radical scavenging and iron-binding/chelating properties. The product represents a functional drink that is capable of alleviating conditions of oxidative stress and iron overload.