Rhodanine assay

Other analytical assays proposed for the quantification of hydrolyzable tannins in plant materials include the rhodanine assay for the estimation of gallotannins (Berardini and others 2004) and sodium nitrate for the quantitative determination of ellagic acid (Wilson and Flagerman 1990). 

The contents of the ampule are diluted in water to a final volume of 50 mL. A 1-mL sample is then taken for the assay. To this sample 1.5 mL 0.667% (w/v) rhodanine in methanol is added. After exactly 5 min. 1 mL 0.5N KOH is added. After 2.5 min. water is added to a final volume of 25 mL. The absorbance is read at 520 nm after a 5-10 min. incubation. A standard curve is made by reaction of gallic acid in 0.2N sulfuric acid with the rhodanine solution. Hagerman and Butler (1989) argued that this assay is more suitable than the potassium iodate assay for the determination of hydrolysable tannins, although it has to be kept in mind that the rhodanine assay is sensitive to any gallic acid ester, including those in non-tannin compounds. 

Moorthy et al. [32] have synthesized 5-isopropylidiene derivatives of 3-dimethyl-2-thio-hydantoin XXVI, 3-ethyl-2-thio-2,4-oxazoIidinedione XXVII, and 5-benzilidene-3-ethyl rhodanine XXVIII, which are cytotoxic against leukemic cell line in concentration-dependent manner. The results of the trypan blue and MTT assays indicated that the compound XXVIII found to be fivefold to sevenfold more potent than XXVI and XXVII with IC5o<10 pM. XXVIII found to affect DNA replication by inducing a block at S phase on the basis of cell cycle analysis and tritiated thymidine assays. Moreover, the treatment of XXVIII led to increased level of reactive oxygen species (ROS) production and DNA strand breaks. This suggests the activation of apoptosis for induction of cell death. 

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