Background: Over the last decade, extensive research work has focused on the potential health benefits of antioxidants while many medicinal plant extracts have been evaluated for their antioxidant profile. Medicinal plants selected for this study are widely used in traditional medicine for the treatment of diabetes mellitus in Sri Lanka some of which are recommended as dietary supplements to the existing therapies. The present study aimed at determining the total polyphenol contents and total antioxidant activities of aqueous extracts of 10 selected Sri Lankan medicinal plants by three in vitro methods; Materials and Methods: DPPH(2, 2-diphenyl-2-picrylhydrazyl), FRAP (ferric reducing power) and NO (nitric oxide) assays. The aqueous plant extracts were tested at the concentration of 0.05 g/mL. The total polyphenol content was determined according to the Folin-Ciocalteu method while the total antioxidant activity was evaluated by DPPH, FRAP and NO assays with L-ascorbic acid as reference compound. Results:The total polyphenol content of the plant extracts varied from 0.41 to 13.00 mg GAE (gallic acid equivalents) per gram dry weight. The antioxidant activities ranged in IC 50 of 36.89-101.27 µg/mL, IC 50 of 139.56-419.93 µg/mL, 0.12-8.98 µM for DPPH, NO, FRAP assays, respectively. A significant positive correlation was observed between total polyphenol content and antioxidant activities (P< 0.05). Conclusion: Phytochemical analysis revealed the presence of polyphenolic compounds, alkaloids and flavonoids in the plant materials which also possessed in vitro antioxidant potentials. Polyphenolic compounds contribute significantly to the total antioxidant capacities of medicinal plant extracts.

tool to overcome issues such as high cost of production, plantation industries. When developing a protocol for ethephon effect on associated latex quality parameters. Therefore, this study elucidated the effect of ethephon on dry rubber yield rheological behaviour and physiological parameters. Five stimulated latex as the control. The results revealed that all the S/2 d3 harvesting system.

The effect of different ethephon concentrations 1%-5% (w/v) on colour of crepe rubber and plasticity retention index (PRI) was studied. The study was conducted with the RRISL 121 clone using S/2, d3 harvesting system. The results revealed that ethephon stimulation affects strongly the antioxidant and polyphenol oxidase (PPO) inhibitory potential. Further, thiol content and PRI values were increased while giving low Lovibond colour index upto 3% ethephon concentration and the properties were found to be inferior above 3% concentration. A probable reaction mechanism is proposed for colour improvement with optimum concentration of ethephon.

Objective of this study was to investigate the effect of different preservative systems used in the concentrated latex manufacturing industry on physical properties of the latex crepe made out of them. Unfractionated and unbleached (UFUB) crepe rubber manufactured from latices preserved with ammonia, tetramethylthiuram disulphide, zinc oxide and a 1:1 mixture of tetramethylthiuram disulphide (TMTD) and zinc oxide (LATZ) were subjected to examine their raw rubber properties. It was observed that UFUB crepe rubber manufactured out of either ammonia preserved, ZnO preserved or chemically untreated latices have better resistance to thermo-oxidative degradation compared to UFUB crepe rubber made out of both TMTD and LATZ preserved latex. Further, it was observed that neither ammonia nor ZnO has any effect on the thermal degradation of crepes made out of ammonia or ZnO preserved latex. It was clear from the results that the TMTD added as a component of the preservative system adversely affects the resistance to thermooxidative degradation as judged by PRI of crepe produced. Crepe rubber manufactured from TMTD preserved latex exhibits unusually lower PRI and a nitrogen content comparable with the normal UFUB crepe rubber. Skim crepe rubber which is considered a by-product of the latex centrifuging industry, usually records higher nitrogen percentages and lower PRI values. Therefore, evaluation of these two parameters could be used to differentiate skim crepe rubber from normal UFUB crepe rubber. It was also observed that TMTD has a strong negative impact on PRI of crepe rubber even at very low concentrations. It could be proposed that dimethylthiuram monosulphide (DMTMS) free radicals generated by thermal decomposition of TMTD are responsible for this PRI reduction.