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A number of O-alkylated xanthone, carbazoles and coumarins have been synthesised and screened for their in vitro anti-diabetic activity, such as glucose-6-phosphatase, glycogen phosphorylase and alpha glucosidase inhibitors. Compounds which were showing significant percentage inhibition were also tested for in vivo anti-hyperglycemic activity in sucrose loaded normal and streptozotocin (STZ)-induced diabetic rats. These compounds show 22.1, 24.4 and 26.7% and 20.8, 25.0, 20.5% lowering in sucrose loaded normal rats and STZ-induced diabetic rats at a dose of 100 mg kg(-1).

To explore the transcriptional control of phenylpropanoid pathway (PPP) involved in vanillin flavour metabolites production in tuberous roots of , four PPP key genes expressed during the tuber development were identified and their mRNA expression profiles were evaluated using quantitative real-time PCR. Flavour metabolite quantification by HPLC analysis confirmed 10, 170 and 500 µg/g 2-hydroxy-4-methoxy benzaldehyde and 4, 20 and 40 µg/g vanillin in first- (3-month-old plant), second- (18-month-old plant) and third-stage tubers (60-month-old matured plant), respectively. The expression of all four genes phenylalanine ammonia lyase (DhPAL), cinnamate-4-hydroxylase (DhC4H), caffeic acid--methyltransferase (DhCOMT) and vanillin synthase (DhVAN) increased with flavour development from first stage to second stage. A decrease in expression from 1.9-folds to 0.1-folds and 19.2-folds to 5.2-folds for and was recorded for second stage to third stage, respectively. However, a gradual increase in expression of (up to 26.4-folds) and a constant expression pattern for (up to 7.1-folds) was evident from second stage to third stage of flavour development. The decrease in the expression levels of and in third stage shows that the second-stage tubers are more transcriptionally active towards flavour biosynthesis.