Antioxidant and Vascular Relaxation Activities of Tropical Plant Extracts

In this study, the methanolic extracts of twelve plants which are the leaves of noni (Morinda citrifolia L.), maman (Gynandropsis gynandra L.), cashew (Anacardium occidentale L.), sweet potato (Ipomoea batatas L.), papaya (Carica papaya L.), mint (Mentha arvensis L.), semambu (Azadirachta indica), betel (Piper betle L.); lemongrass stalk (Cymbopogon citrates Stapf.), bird chili fruit (Capsicum frutescens L.), roselle calyx (Hibiscus sabdariffa), and oil palm frond (Elaeis guineensis Jacq.) were analyzed for in vitro antioxidant and vascular activities. Their total phenolic content was also estimated. Plant extract showing high antioxidant and vascular relaxing activities were further tested for their in vivo antioxidant and cholesterol lowering effects in hypercholesterolemic New Zealand White rabbits.In vivo antioxidant test (ferric reducing/antioxidant potential [FRAP] assay) showed the highest activity in cashew leaf extract (4.3 mmol FRAP/g d.w.) and the lowest in lemongrass extract (0.2 mmol FRAP/g d.w). The antioxidant activity of the cashew leaf extract was equivalent to those of green tea extract while lemongrass extract's antioxidant activity was equivalent to those of purified apigenin. The total phenols ranged from 55-256 mg gallic acid equivalent / g dry weight (d.w.) extracted samples with the highest concentration in oil palm frond extract. In this study, the antioxidant activity of the extracts did not correlate with the total phenolic contents, mainly due to the heterogeneity of the samples tested. For vascular activity, sweet potato, betel, cashew, maman, mint, oil palm frond, semambu, bird chili, and papaya extracts showed more than 50% relaxing effects in Wistar Kyoto rat's isolated aortic ring preparation. Most of the relaxing effects were endothelium-dependent with nitric oxide as the main mediator. Prostacyclin and endothelium-derived hyperpolarizing factors (EDHF) effects were also observed in small amounts. For the smaller vessels, mesenteric arteries, the extent of relaxation is reduced, where only oil palm frond, betel and lemongrass extracts showed more than 50% relaxing effect. It is observed that in the smaller vessel, the EDHFs effects are more prominent, especially in the betel and lemongrass extracts. Oil palm frond was selected for the in vivo study for its high phenolic content and high vascular relaxing activities in both blood vessel preparations. This study showed that oil palm frond supplementation in the diets of hypercholesterolemic rabbits led to a delayed increment in serum total cholesterol levels. There was no significant antioxidant and toxicity effect on liver, kidney and muscle observed. This study shows that most of the selected plants possess a high antioxidant and vascular relaxing activities. Antioxidants in food are important in minimizing food deterioration i.e. rancidity which affect the taste and textures of food containing lipids. In human, dietary antioxidants help to reduce oxidative stress, which is associated with the etiology of several chronic diseases such as hypertension, cancer, aging diseases, atherosclerosis and coronary artery diseases. Similarly, consumption of plants possessing vascular relaxing activities may restore and/or improve vascular functions and hence protect against vascular diseases such as hypertension

Bioavailability of Phytochemicals

Phytochemicals are increasingly accepted as health promoting, maintaining, and repairing agents in cells, tissues, or the whole human body. Phytochemicals are compounds obtained from plants that exert particular health effects; generally, they are not necessarily basic nutrients (minerals, vitamins, carbohydrates, proteins or lipids), medicines or toxins. The phytochemicals that are frequently associated with human health are phenolics, carotenoids, organic acids, and several miscellaneous bioactive compounds such as saponin and sterols. The contributions of phytochemicals in public health cover various issues world-widely and thus it is seen by researchers, industries, general society, and policy makers as a new tool to manage public health. Ironically, the roles of phytochemicals in health are poorly understood, which warrant the needs for validation as well as scientific database on safety issues and mechanisms of the functions. Even though various genetic-base studies propose mechanisms and health interventions of phytochemicals (Noe et al., 2004), many findings are inconclusive. Hence, the emerging health potentials of phytochemicals are inconclusive; and internationally it has been the reason for new policies/regulations in food trading. This is partly due to limited understanding on phytochemical bioavailability by which the health benefits depend on. Moreover, transport mechanisms for phytochemicals delivery into the target sites, phytochemical metabolisms by the human body, and biomarkers exerting the health benefits are also poorly understood. These complexities call for a new framework on how and to what extent dietary phytochemicals should be recommended in order to reach biologically-safe active dosages. In the human body, bioavailability is defined as substances obtained from ingested materials that reach circulatory system for further delivery into designated tissues so that the beneficial compounds are biologically available for exerting healthy functions. The normal routes of dietary phytochemicals thus include ingestion, digestions, and transport across gastrointestinal epithelium prior to circulatory vessels. The epithelium in the gastrointestinal tract is a polarized enterocyte cell having two different sides facing luminal hollow (Apical side) and blood capillaries (Basolateral side) where each side is equipped with different transport facilities and barriers. The epithelial cells are critical for bioavailability of target compounds either as entrance gates or as metabolizing machines which release different compounds from the parent molecules. These make further complexing bioavailability routes because the metabolisms and transport processes are also involved in the orchestrated physiological regulations maintaining homeostasis states of the human body. However, bioavailability of phytochemicals by which the health benefits depend on are not well understood; consequently, it is difficult to be measured. The difficulties in studies of bioavailability are mainly due to the complexities involved in the biological system, i.e. (a) variation in food materials and the human subjects or surrogate models which are not always representative; (b) complex interactions amongst huge chemicals/food components during postharvest, storage, processing, digestion, and absorption that may alter health benefits; and (c) mechanism pathways. In this paper, fundamental aspects of phytochemical bioavailability are reviewed

Optimization of Total Flavonoid Compound Extraction from Gynura medica Leaf Using Response Surface Methodology and Chemical Composition Analysis

Optimization of total flavonoid compound (TFC) extraction from Gynura medica leaf was investigated using response surface methodology (RSM) in this paper. The conditions investigated were 30–60% (v/v) ethanol concentration (X1), 85–95 °C extraction temperature (X2) and 30–50 (v/w) liquid-to-solid ratio (X3). Statistical analysis of the experiments indicated that temperature and liquid-to-solid ratio significantly affected TFC extraction (p < 0.01). The Box-Behnken experiment design showed that polynomial regression models were in good agreement with the experimental results, with the coefficients of determination of 0.9325 for TFC yield. The optimal conditions for maximum TFC yield were 55% ethanol, 92 °C and 50 (v/w) liquid-to-solid ratio with a 30 min extraction time. Extracts from these conditions showed a moderate antioxidant value of 54.78 μmol quercetin/g dry material (DM), 137.3 μmol trolox/g DM for 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 108.21 μmol quercetin/g DM, 242.31 μmol trolox/g DM for 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS+), respectively. HPLC-DAD-MS analysis showed that kaempferol-3-O-glucoside was the principal flavonoid compound in Gynura medica leaf

Phenolic compound profiles in selected Queensland red wines at all stages of the wine-making process

The phenolic profiles of Queensland red wines (two Cabernet Sauvignons and one Shiraz) from different stages of wine-making were studied. Samples were taken at crush, after the primary and malolactic fermentations, post-oaking, and post-bottling, and then extracted and separated into aqueous and organic fractions using liquid liquid extraction and solid-phase extraction, and analysed by HPLC-DAD-MS. About 75% of the phenolic compounds were extracted into the aqueous fraction, with malvidin-3-glucoside and derivatives as the main components. The major non-anthocyanin phenolic compounds (similar to 25%) included gallic acid, syringic acid, ethyl gallate, caftaric acid, coutaric acid, caffeic acid, coumaric acid, catechin, and quercetin. The polymerisation of anthocyanins was shown to occur progressively throughout the wine-making process. Most of the 25 identified phenolic compounds had highest concentrations during the fermentation stage, and stabilised or slowly decreased thereafter. There were weak and insignificant correlations (P > 0.05) between individual phenolic compounds and the total antioxidant activities (ORAC). Four groups of phenolic compounds (anthocyanins, hydroxybenzoic acids, flavanols and hydroxycinnamic acids) each showed some correlation with the total antioxidant activity, as did the total polyphenol content, suggesting that the antioxidant properties of red wine are due to a complex mixture of phenolic compounds that vary in composition throughout the wine-making process. (C) 2010 Elsevier Ltd. All rights reserved

DNA damage inhibitory effect and phytochemicals of fermented red brown rice extract

Objective: To determine the polyphenol compounds (phenolic and flavonoid compounds), antioxidant activity [1,1-diphenylpicryl-2-picrylhydrazyl (DPPH) radical scavenging activity] and DNA damage inhibitory effect of fermented local red brown rice. Methods: DNA nicking assay was employed to determine the antioxidant activity of the fermented rice extract. Phytochemical screening was completed using standard methods and DPPH radical assays were used to confirm the antioxidant properties of the extracts. Results: After four days of fermentation, fermented red brown rice had more polyphenol compounds compared to unfermented counterpart. Fermented red brown rice showed greater antioxidant properties with EC<inf>50</inf> value of DPPH radical scavenging of 43.00 mg extract/mL or 8 mg quercetin equivalent antioxidant activity. In addition, fermented rice extract showed DNA damage inhibitory effect to a certain extent. It protected DNA from reactive oxygen species; however, at high concentration it might induce reductive damage to DNA, whereas, unfermented red brown rice showed weak DNA damage inhibitory effect. Conclusions: Fermented red brown rice could protect DNA from oxidative damage but might induce reductive damage to DNA at high concentrations

Phenolic contents and antioxidant activities of major Australian red wines throughout the winemaking process

Three Australian red wine types (Shiraz, Cabernet Sauvignon, and Merlot) were analyzed for antioxidant activity and a range of phenolic component contents using various spectral methods. More than half of the total phenolic compounds were tannins, whereas monomeric anthocyanins and flavonols were present in much lesser amounts

Screening Sarawak Caves for urease producing bacterial strains and evaluating their efficiency in calcium carbonate precipitation

Microbially induced calcite precipitation (MICP) is a naturally occurring biological process that has emerged as an attractive alternative ground improvement technique in Geotechnical and Civil engineering for soil strengthening and stabilization. MICP utilizes urease producing bacteria (such as Sporosarcina pastuerii, formally known as bacillus pastuerii) to catalyse the hydrolysis of urea for the production of ammonium and carbonate ions, which react with calcium ions (e.g. calcium chloride) to form calcium carbonate (calcite) that binds soil particles together, therefore increasing soil shear strength and stiffness. This study aimed at isolating urease producing bacteria from Sarawak limestone caves with the potential of precipitating calcite. A total of 28 bacterial strains were isolated from the enriched medium. Out of these isolates, 2 bacterial strains were selected based on their quick urease production. Their urease activities were assayed through changes in conductivity while their specific urease activity were calculated as the amount of urease activity per unit biomass

Characterisation of urease producing bacteria from sarawak caves and their role in calcite precipitation

Abstract not available