MATERIALS AND METHODS: Total phenolic content (TPC) and ascorbic acid equivalent antioxidant capacity (AEAC) were assessed using the Folin-Ciocalteu and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, respectively. Minimum inhibitory dose (MID) against Gram-positive Micrococcus luteus, Staphylococcus aureus, and Bacillus cereus, and Gram-negative. Escherichia coli, Salmonella typhi, and Pseudomonas aeruginosa was assessed using the disc-diffusion method. Teas were extracted with hot water successively three times for one hour each time. The extracts were fractionated using Sephadex LH-20 column chromatography to obtain the NP and PT constituents.
RESULTS: Extraction yields ranged from 12 to 23%. Yields of NP fractions (70-81%) were much higher than those of PT fractions (1-11%), suggesting that the former are the major tea components. Ranking of antioxidant properties of extracts was green tea>black tea>herbal tea. For all six teas, antioxidant properties of PT fractions were significantly higher than extracts and NP fractions. Extracts and fractions of all six teas showed no activity against the three Gram-negative bacteria. Green teas inhibited all three Gram-positive bacteria with S. aureus being the least susceptible. Black and herbal teas inhibited the growth of M. luteus and B. cereus, but not S. aureus. The most potent were the PT fractions of Boh Cameron Highlands and Ho Yan Hor with MID of 0.01 and 0.03 mg/disc against M. luteus.
CONCLUSION: Results suggested that NP constituents are major contributors to the antioxidant and antibacterial properties of teas of C. sinensis. Although PT constituents have stronger antioxidant and antibacterial properties, they constitute only a minor component of the teas.
METHODS: They have also been used for antibacterial, antifungal, anticancer, antitubercular activities. Novel synthesised Schiff's base 2-methoxy-4-((3-methylpyridin-2-ylimino)methyl)phenol (SB) and its metal complexes (Zn[II], Cu[II], Co[II] and Ni[II]) were characterised by UV, IR and NMR spectroscopy. Formation of the Schiff base and the metal (Zn[II], Cu[II], Co[II] and Ni[II]) chelates was supported by spectral and analytical data. The ligand and metal complexes have been screened for their antibacterial activity against Staphylococcus aureus, Salmonella typhi, Escherichia coli, Klebsiella pneumoniae and antifungal activity against the fungi Candida albicans and Aspergillus niger. Further, the synthesised compounds were also screened for antiproliferative activity against the human colorectal carcinoma (HCT116) cell line using the Sulforhodamine B assay.
RESULT: Metal complexes formed were found to enhance the potency of the Schiff base due to coordination with a copper complex, showing better activity than others.
CONCLUSION: Copper complex was observed to be more potent than other complexes against all the pathogenic microbes and cancer cell line (HCT116).