Seong-Gook Kang

In vitro studies of polyphenols, antioxidants and other dietary indices in kiwifruit (Actinidia deliciosa)

The main aim of the present study was the evaluation of proteins and antioxidant potential in ethylene-treated kiwifruit during the first 10 days of ripening. Kiwifruit samples were randomly divided into two groups: treated and untreated. Flesh firmness, sensory value, visual score, free sugars, soluble solids, ethylene biosynthesis, proteins, dietary fibers, total polyphenols and antioxidant potential were determined in both groups. Ethylene (100 ppm) at 20°C for 24 h was used in the treated group. The flesh firmness and acidity in treated samples decreased significantly in the early stage of ripening simultaneously with significant increase in the contents of free sugars, soluble solids, endogenous ethylene production, sensory value, 1-aminocyclopropane-1-carboxylic acid (ACC) content, ACC synthase and ACC oxidase activities, total polyphenols and related antioxidant potential, and was significantly higher than in untreated samples (P < 0.05). Proteins were extracted from kiwifruit and separated by modified sodium dodecyl sulphate polyacrylamide gel electrophoresis. The separation was resolved into 14 protein bands. Some minor quality changes were found only in the 32 kDa band, which was more pronounced in the treated samples. In conclusion, ethylene treatment of kiwifruits leads to positive changes in most of the studied kiwifruit compounds and to an increase in the fruit antioxidant potential. It shortens the ripening time and improves fruit quality by decreasing its flesh firmness and acidity. Some minor changes in the protein profile did not affect the fruit taste and quality.

Nutritional and Pharmaceutical Properties of Bioactive Compounds in Organic and Conventional Growing Kiwifruit

The bioactivity of two kiwifruit’s cultivars growing under organic and conventional conditions were studied and compared. The bioactive compounds were extracted with water and ethanol using similar conditions which are applied in pharmaceutical applications and for daily fruit consumption such as tea drink. Antioxidant radical scavenging assays [ferric-reducing/antioxidant power (FRAP); cupric reducing antioxidant capacity (CUPRAC); 2, 2-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS)], fourier transform infrared (FT-IR) and ultraviolet spectroscopy, two (2D-FL) and three-dimensional (3D-FL) fluorometry were used for the detection of biologically active metabolites derived from kiwifruits (total phenols, flavonoids, chlorophylls, carotenoids and ascorbic acid). The correlation between the total phenol content (TPC) and other bioactive compounds, and their total antioxidant capacities (TAC) was calculated for studied kiwifruit’s extracts. The interaction between drugs and human serum albumin (HSA) plays an important role in the distribution and metabolism of drugs. The properties of kiwifruit’s phenol extracts showed their ability to quench HSA, forming the complexes similar to the ones between the proteins and pure flavonoids such as quercetin. The cultivar ‘Bidan’ exhibited significantly higher TAC than the classic ‘Hayward’. In conclusion, for the first time ‘Bidan’ organic kiwifruit was analyzed and compared with widely consumed ‘Hayward’, using its bioactive and fluorescence properties. The influence of physiologically active kiwifruit’s compounds on human health, through our investigations in vitro and scientifically proven information, was explained. Relatively high content of bioactive compounds, high antioxidant and fluorescence properties of kiwifruit justify its use as a source of valuable antioxidants.

Screening of the antioxidant and nutritional properties, phenolic contents and proteins of five durian cultivars

The antioxidant activities of different durian cultivars at the same stage of ripening (Mon Thong, Chani, Kan Yao, Pung Manee and Kradum) were compared in order to choose the best as a supplement in the human diet. Total polyphenols (mg gallic acid equivalent/100 g fresh weight (FW)) and flavonoids (mg catechin equivalent (CE)/100 g FW) in Mon Thong (361.4±23.2 and 93.9±7.4) were significantly higher (P<0.05) than in Kradum (271.5±11.2 and 69.2±5.3) and Kan Yao (283.2±16.5 and 72.1±6.8). The free polyphenols and flavonoids showed lower results than the hydrolyzed ones. Anthocyanins (µg cyanidin-3-glucoside equivalent/100 g FW) and flavanols (µg CE/100 g FW) were significantly higher in Mon Thong (427.3±23.8 and 171.4±16.3) than in Kradum (320.2±12.1 and 128.6±9.7) and Kan Yao (335.3±14.1 and 134.4±11.7). Ultraviolet spectroscopy and high-performance liquid chromatography/diode array detection analyses showed that caffeic acid and quercetin were the dominant bioactive substances in Mon Thong cultivar. The antioxidant activity (µM trolox equivalent/100 g FW) of Mon Thong cultivar (260.8±20.2, 1,075.6±81.4 and 2,352.7±124.2) determined by ferric-reducing/antioxidant power (FRAP), cupric reducing antioxidant capacity (CUPRAC) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) with Trolox equivalent antioxidant capacity (TEAC) assays was significantly higher (P<0.05) than in Kradum (197.4±8.9, 806.5±31.2 and 1,773.2±102.5) and in Kan Yao (204.7±9.7, 845.5±48.6 and 1,843.6±107.5). The correlation coefficients between polyphenols, flavonoids, flavanols and FRAP, CUPRAC and TEAC capacities were between 0.89 and 0.98. In extracted and separated by electrophoresis durian proteins, some differences were found in the sodium dodecyl sulfate–protein bands in the region of 16 and 68 kDa for Kradum, 45 kDa for Mon Thong and three bands for Kan Yao. Antioxidants and proteins can be used for characterization of the quality of durian cultivars. In conclusion, the bioactivity of durian cultivars Mon Thong, Chani and Pung Manee was high and the total polyphenols were the main contributors to the overall antioxidant capacity. The results of our investigation in vitro are comparable with other fruits that widely used in human diets. Therefore, Durian can be used as a supplement for nutritional and healthy purposes, especially Durian Mon Thong, Chani and Pung Manee.

Comparison of the Nutrient and Chemical Contents of Traditional Korean Chungtaejeon and Green Teas

This study was conducted in order to compare the nutrient and chemical contents of two Korean teas: traditional Chungtaejeon tea (CTJ) with that of green tea (GT). Main bioactive compounds and the antioxidant activities using four radical scavenging assays (ABTS, CUPRAC, FRAP and DPPH) in methanol and acetone extracts of both teas were determined. It was found that the contents of vitamin C, amino acids and total nitrogen in CTJ were lower than that of GT (p < 0.05). Caffeine, reducing sugar and chlorophyll contents in CTJ were similar to GT. Catechin (C), epicatechin (EC), and epigallocatechin (EGC) contents were lower in CTJ than in green tea (p < 0.05), but gallocatechin (GC), epicatechin gallate (ECG), epigallocatechin gallate (EGCG) and catechin gallate (CG) showed no significant differences between CTJ and GT (p ≥ 0.05). The contents of polyphenols, flavonoids, flavanols and tannins in CTJ methanol were 229.30 ± 11.3 mg GAE/g dry weight (DW), 15.24 ± 0.8 mg CE/g DW, 109.10 ± 5.1 mg CE/g DW and 25.68 ± 1.2 mg CE/g DW, respectively, and significantly higher than in acetone extracts (p < 0.05). Flavonoids (quercetin and kaempferol) were higher in GT than in CTJ and myricetin was higher in CTJ (p < 0.05). Threonine and aspartic acid was lower, and glutamic acid was higher in CTJ compared with GT (p < 0.05). Free amino acid content in CTJ and GT showed no significant difference. Potassium and magnesium in CTJ were lower compared to GT, but no significant difference was found for iron, manganese and calcium. Also, the level of the antioxidant activity by all four used assays was significantly higher in CTJ and in methanol was higher than in acetone extracts (p < 0.05). In conclusion, traditional fermented Korean tea Chungtaejeon contains high quantities of bioactive compounds and possesses high antioxidant activity. The contents of the bioactive compounds and the levels of antioxidant activities are significantly higher in methanol than in acetone extracts. 3-D fluorescence and FTIR- spectroscopy showed slight differences between the two investigated tea samples and can be used as additional tools for identification of polyphenols. Both studied teas can be recommended as a source of bioactive compounds.

In vitro Antioxidant Potential and Inhibitory Effect of Seaweed on Enzymes Relevant for Hyperglycemia

Hizikia fusiforme, Capsosiphon fulvescens, Undaria pinnatifida sporophyll, and Undaria pinnatifida blade extracts were evaluated for in vitro antioxidant and antihyperglycemic activities. Seaweed extracts contained high levels of phenolic compounds (12.44 to 39.01 mg of gallic acid equivalents/g of extract) and exhibited multiple antioxidant activities. Extracts showed weak inhibition of α-amylase. However, all extracts showed pronounced inhibition of α-glucosidase with EC50 values from 2.56 to 18.81 mg/mL. U. pinnatifida sporophyll and U. pinnatifida blade extracts both contained protocatechuic and syringic acids. p-Coumaric and ferulic acids were detected only in the H. fusiforme extract. Caffeic acid and epicatechin were the dominant phenoilc acids found in C. fulvescens extracts. A basis for further research is provided to establish the capability of seaweed extracts as hypoglycemic agents or functional food ingredients.

Effect of long-term cold storage on physicochemical attributes and bioactive components of kiwi fruit cultivars

Various kiwi fruit cultivars, bred in Korea, were kept in cold storage for 8–24 weeks for possible increase of their quality. Firmness significantly decreased at initial time in all cultivars. The rate of softening was the slowest in “Hayward”, followed by “Hort 16A”, “Haenam”, “Daheung”, “Bidan”, “Hwamei”, and “SKK 12”. Sensory value increased with decreasing of firmness. Soluble solids content increased with storage time while acidity gradually decreased. Reducing sugar content significantly increased at early stage of storage with decreasing of starch content. There was no difference of these indices among cultivars. Respiration rate increased with time and then decreased during cold storage. Peaks time was different between cultivars, therefore we represented trend of respiration changes in all cultivars. All kiwi fruit cultivars showed climacteric patterns in respiration. The rate of softening was closely related to the degree and peak time of ethylene production. The highest shelf life was in “Hayward” and “Hort 16 A” (24 weeks) and the lowest in “SKK-12” (8 weeks). All investigated cultivars bred in Korea showed much lower shelf life than “Hayward” and “Hort 16 A”. Radical scavenging assays and chemometrical processing were used for the determination of bioactive kiwi fruits’ compounds. Polyphenols in water extracts were the highest in “SKK-12” and the lowest in “Hayward” [16.34 ± 1.11 and 5.30 ± 0.45 mg gallic acid equivalents (GAE)/g dry weight (DW)]. The values of β-carotene activities (27.61 ± 2.44% and 8.33 ± 0.74%) and Ferric-reducing/antioxidant power [(FRAP, Trolox equivalent (TE)/g DW) 24.55 ± 2.01 and 7.12 ± 0.41] were the highest in “SKK-12”. The lowest results were estimated in “Hayward”. All kiwi fruit cultivars showed a high level of correlation between the contents of phenolic compounds (polyphenols, tannins, and flavonoids) and their antioxidant values. We presented for the first time the results of shelf life of new cultivars bred in Korea and their comparison with the widely studied ones, such as “Hayward” and “Hort 16A”. Cold storage extended shelf life in kiwi fruit without any chilling injury or color change. According to the antioxidant properties of different cultivars, the highest was in “SKK-12” with the lowest shelf life and the lowest was in “Hayward” with the highest shelf life.

Aorta and liver changes in rats fed cholesterol-containing and raw vegetable-supplemented diets: experiments in vitro and in vivo.

The aim of this investigation was to compare the liver and aorta changes in rats fed cholesterol-containing diets and the possible improvement when diets would be supplemented with frequently used raw vegetables. The phenolic compounds of three vegetables in methanol-water (1:1) fraction were characterized using electrospray ionization mass spectra (ESI-MS). Results showed that the content of polyphenols, flavonoids, quercetin, flavanols, tannins, and ascorbic acid varied for garlic and white and red onions ranging from 6.68 to 18.08 mg GAE/g DW, 490.4-701.0 μg CE/g DW, 281.2-1100.0 μg, 32.40-41.30 μg CE/g DW, 2.88-3.12 mg CE/g DW, 1.87-2.33 mg AA/g DW, 1388.2-1442.3 μg CGE/g DW, respectively. The radical scavenging capacities (μM TE/g DW) for the same investigated vegetables for ABTS, FRAP, CUPRAC, and DPPH assays ranged from 48.78 to 92.42, 9.41-28.56, 3.06-10.41, and 6.49-23.42, respectively. Good correlations were observed between the phenolic contents and the radical scavenging capacities of the vegetables. The interaction between BSA and quercetin, BSA and garlic and onions extracts was measured by 3-dimensional fluorescence (3D-FL) and Fourier transform infrared (FT-IR) spectroscopy. The highest polyphenol content was found in methanol/water fraction of onions and garlic; therefore, for the investigation of in vitro interactions with BSA only polyphenols of this fraction were used. For in vivo studies, 30 male Wistar rats were divided into 5 groups each of 6 and named Control, Chol, Chol/Garlic, Chol/OnionRed, and Chol/OnionWhite. During 6 weeks, the rats of all 5 groups were fed a basal diet (BD). The rats of the Control group were fed the BD only. The BD of the Chol group was supplemented with 10 g/kg of nonoxidized cholesterol (NOC). Each of the other three groups was supplemented with 10 g/kg of NOC and 500 mg of raw fresh garlic, 500 mg of raw fresh red onion, and 500 mg of raw fresh white onion on 1 kg of body weight for Chol/Garlic, Chol/OnionRed, and Chol/OnionWhite diet groups, respectively. In order to detect the changes in the liver and aorta, a histological procedure was applied, and the liver enzymes were determined and compared. It was found that the main changes vs the Control group were in the liver of rats fed the cholesterol-containing diet without vegetable supplementation. Significantly less histological changes in the liver and lower level of liver enzymes vs those of the Chol group were detected in rats of the Chol/Garlic group (P < 0.05). The interaction between the polyphenol extract of garlic and BSA in vitro showed its strong ability comparable with that of quercetin to quench the intrinsic fluorescence of BSA. In conclusion, all studied vegetables showed protective effects, but raw garlic supplemented with cholesterol-containing diets significantly prevented the aorta and liver damages of rats.

In vitro antioxidative and binding properties of phenolics in traditional, citrus and exotic fruits☆

Many polyphenols bind proteins, therefore our research was focused on the potential of protein binding to polyphenols of investigated fruits and their health-related effects. The contents of polyphenols and related antioxidant activities of traditional, citrus and exotic fruits were compared. The presence of polyphenols (flavonoids and phenolic acids) in the investigated samples and their interaction with human serum albumin (HSA) was studied by HPLC, Fourier Transform Infrared (FT-IR) and three dimensional fluorescence spectroscopy (3D-FL). The highest levels of polyphenols, antioxidant and binding capacities were found in red and blond grapefruits (citrus group), followed by strawberries and apples (traditional group) and mangosteen and kiwi fruit (exotic fruit), which also contained the highest levels of protocatechuic, p-coumaric, ferulic acids and quercetin. In conclusion, for the first time, the interaction of the polyphenols with human serum albumin was evaluated by fluorometry/FTIR. The obtained binding profiles allowed the comparison of three different groups of fruits. A mixture of these fruits can be recommended for consumption.

Antithrombotic potential of extracts from abalone, Haliotis Discus Hannai Ino: In vitro and animal studies

To screen the more promising antithrombotic abalone extracts, the in vitro antithrombotic activity of 6 abalone (Haliotis Discus Hannai Ino) extracts was examined in this study. Results of in vitro studies indicated that water extract of abalone viscera (WEV) presented significant longer prothrombin time (PT), partial thromboplasmatin time (APTT), and thrombin time (TT) than other abalone extracts. In addition, the platelet aggregation process was inhibited by WEV as well. The antithrombotic potential of WEV was further investigated in animal studies which revealed that WEV prolonged tail bleeding time, APTT but not PT and TT and showed no effect on the platelet aggregation and platelet number. The WEV treated rats presented lower cholesterol and triglyceride level than the control group although the difference was not statistically significant. Results of this study indicate the antithrombotic activity of abalone extracts, especially WEV, and may contribute to the further study in this field.

Rapana venosa as a bioindicator of environmental pollution

The aim of this investigation was to examine biochemical differences in the gastropod Rapana venosa (R. venosa) from polluted (RvP) and nonpolluted (RvN) sites of the Black Seas Bulgarian coast that may serve as bioindicators of environmental quality. Mussels Mytilus galloprovincialis (MMg) were collected from polluted (MMgP) and nonpolluted (MMgN) sites at the same time for comparison. Bioactive compounds and the antioxidant activity of dry matter (DM) methanol extracts from RvP and RvN were determined. Three-dimensional fluorometry (3D-FL) and Fourier transform infrared (FTIR) analyses were used to evaluate polyphenols and proteins. DM methanol extracts from RvP, and to lesser extent RvN, showed high amounts of total phenolics (23.22±2.9 and 15.60±1.8 mg GAE · g−1 DW) and exhibited high levels of antioxidant activity in some radical scavenging assays (μ MTE · g−1 DW): 56.38±5.2 and 33.79±3.3 by 2,2azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) diamonium salt (ABTS·+); 54.79±5.6 and 33.7±2.6 by cupric reducing antioxidant capacity (CUPRAC); 62.34±6.8 and 30.31±3.9 by the 1diphenyl-2-picrylhydrazyl method (DPPH). A correlation in the above indices was found between R. venosa and M. galloprovincialis, but all results were relatively higher for M. galloprovincialis than for R. venosa. The obtained indices of R. venosa may serve as a bioindicator of environmental ecological quality.