Thermostability and catechol-O-methyltransferase inhibitory activity of acylated anthocyanins from purple yam

The thermostability of purple yam were investigated to be used as natural colorants. In addition, the inhibitory properties of purple yam and its isolated anthocyanins toward human catechol-O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression, were also investigated. The thermostability of purple yam was higher than that of the reference samples (purple sweet potato and purple potato). Quantitative HPLC analysis revealed that alatanin A (2) contributed to the thermostability of purple yam. Methanol extracts of purple yam exhibited the highest COMT inhibitory activity of the tested samples. Alatanin D (1) showed the highest inhibitory activity of the anthocyanins in purple yam (IC50 19 μM). This study revealed the thermostability and COMT inhibitory activity of purple yam and may lead to its use not only as a thermostable natural source of colorants but also for the prevention and treatment of Parkinson's disease and depression.