Antioxidant and free radical scavenging activities of wild bitter melon (Momordica charantia Linn. var. abbreviata Ser.) in Taiwan

Momordica charantia Linn. var. abbreviata Ser. (Cucurbitaceae), also known as “Shan Ku Gua”, is a wild variety of bitter melon (BM) in Taiwan. The size of its fruits is only about one-fifth of the commonly seen BM. It is commonly consumed as vegetable and also used as a popular folk medicine. In this study, the antioxidant and free radical scavenging activities of BM aqueous (BM-H₂O) and ethanol (BM-EtOH) extracts were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), metal chelation, cytochrome c and xanthine oxidase inhibition (XOI) assays, as well as FeCl₂-ascorbic acid induced lipid peroxidation (thiobarbituric acid reactive substances, TBARS) assay in rat liver homogenates in vitro. Total flavonoid and phenol contents of BM extracts were also analyzed. Results showed that both BM-H₂O (IC₅₀=129.94 μg/ml) and BM-EtOH (IC₅₀=156.78 μg/ml) possess potent DPPH radical scavenging activity, which was better than vitamin E (IC₅₀=172.21 μg/ml). These extracts also showed better iron chelating activity than vitamin E. However, they were weaker than vitamin E in free radical scavenging, xanthine oxidase inhibitory and anti-lipid peroxidation activities. With the exception of XOI activity [IC₅₀=7.90 μg/ml (BM-H₂O) vs. 7.69 μg/ml (BM-EtOH)], BM-H₂O showed a lower IC₅₀ value in free radical scavenging [IC₅₀=6.15 μg/ml (BM-H₂O) vs. 7.08 μg/ml (BM-EtOH)] and anti-lipid peroxidation [IC₅₀=53.72 μg/ml (BM-H₂O) vs. 88.51 μg/ml (BM-EtOH) for liver; 82.53 μg/ml (BM-H₂O) vs. 91.83 μg/ml (BM-EtOH) for brain] activities than BM-EtOH. Both BM extracts showed a weak anti-lipid peroxidation activity in plasma. BM-H₂O (62.0 mg/g) possessed a significant higher concentration of total flavonoids than BM-EtOH (44.0 mg/g), but was lower in the total phenol content (BM-H₂O: 51.6 mg/g vs. BM-EtOH: 68.8 mg/g). In conclusion, BM extracts possess potent antioxidant and free radical scavenging activities. These antioxidant activities could have contributed, at least partly, to the therapeutic benefits of the certain traditional claims of wild BM.     

Antioxidant and free radical scavenging activities of polyphenol-enriched curry leaf (Murraya koenigii L.) extracts

The in vitro antioxidant properties of different extracts (water, alcohol, alcohol:water, hexane or chloroform extract) of curry leaves (Murraya koenigii L.) were evaluated using various assays. The alcohol:water (1:1) extract of curry leaves (AWEC) showed the highest antioxidant and free radical scavenging activity. It inhibited membrane lipid peroxidation by 76%, at 50 μg/ml, scavenged 93% of superoxides at 200 μg/3 ml and scavenged approximately 90% of hydroxyl and 1,1-diphenyl-2-picrylhydrazayl radicals at 4–5-fold lower concentrations compared to the other tested extracts. In addition, the alcohol:water extract reduced cytochrome c and ferric ion levels, chelated ferrous ions and inhibited ferrous sulfate:ascorbate-induced fragmentation and sugar oxidation of DNA. These results establish the antioxidant potential of AWEC, which could be used as natural antioxidant source.     

In vitro activity of methanol extracts of plants used as spices against Mycobacterium tuberculosis and other bacteria

This study determined the phenolic composition of two thyme species (Lamiaceae), Origanum minutiflorum O. Schwarz and P.H. Davis and Thymbra spicata L. var. spicata, and assessed their antibacterial and antimycobacterial activities. “Kekik” is a collective term used in Turkey for plants that smell like thyme. O. minutiflorum, (locally “Sutculer kekigi”, endemic) and T. spicata var. spicata (locally “Karakekik”) are widely used in Turkey and are important export commodities.     

Antioxidant and free radical scavenging activity of an aqueous extract of Coleus aromaticus

The leaves of Coleus aromaticus Benth., (Lamiaceae), commonly called Indian Borage, are often eaten raw with bread and butter. The chopped leaves are also used as a substitute for sage (Salvia officinalis Linn.) in stuffing. In the present study, the antioxidant potency of freeze-dried aqueous extract of C. aromaticus was investigated, employing various established in vitro systems, such as the β-carotene-linoleate model system, 1,1-diphenyl-2-picrylhydrazyl (DPPH)/superoxide/nitric oxide radical scavenging, reducing power, and iron ion chelating activity. Freeze-dried aqueous extract of C. aromaticus (CAE) showed notable inhibitory activity in the β-carotene-linoleate model system. Furthermore, CAE exhibited a moderate concentration-dependent inhibition of the DPPH radical. The multiple antioxidant activity of CAE was evident as it showed significant reducing power, superoxide scavenging ability, nitric oxide-scavenging activity and also ferrous ion chelating potency. The data obtained in the in vitro models clearly establish the antioxidant potency of freeze-dried extract of C. aromaticus.     

Antioxidant and free radical scavenging activities of phenols from onion (Allium cepa)

Four (red, violet, white and green) varieties of Allium cepa were studied for their total phenolic contents (TPC), antioxidant (AOA) and free radical scavenging activities (FRSA). The TPC varied from 4.6 to 74.1 mg/g GAE, AOA varied from 13.6% to 84.1% and FRSA showed wide range in terms of IC₅₀ (inhibitory concentration) from 0.1 to 15.2 mg/ml, EC₅₀ (efficient concentration) from 4.3 to 660.8 mg/mg and ARP (antiradical power) from 0.15 to 23.2. The outer dry layers of red and violet varieties showed better inhibition of lipid peroxidation assayed by ammonium thiocyanate than α-tocopherol. The non-site-specific inhibition of hydroxyl radical induced deoxyribose degradation was also higher in the outer dry layers of red and violet varieties than in their middle and inner layers. The outer layers were also potential inhibitors of nitroblue tetrazolium chloride (NBT) reduction caused by superoxide anions. On the other hand the ferrous ion chelating capacity of the red and violet varieties was highest in the inner layers. Specific phenolic composition performed through HPLC and LC–MS/MS showed the presence of gallic acid, ferulic acid, protocatechuic acid, quercetin, and kaempferol. The unutilised outer layers of the red variety were a rich source of quercetin (5110 μg/g) with high AOA, FRSA and also showed significant protection of DNA damage caused by free radicals.     

Antioxidant and antibacterial activities of Nephelium lappaceum L. extracts

Ether, methanolic and aqueous extracts of lyophilized rambutan (Nephelium lappaceum L.) peels and seeds were evaluated for phenolic contents, antioxidant and antibacterial activities. High amounts of phenolic compounds were found in the peel extracts and the highest content was in the methanolic fraction (542.2 mg/g dry extract). Several potential antioxidant activities, including reducing power, β-carotene bleaching, linoleic peroxidation and free radical scavenging activity, were evaluated. The peel extracts exhibited higher antioxidant activity than the seed extracts in all methods determined (P < 0.05). The methanolic fraction was found to be the most active antioxidant as shown by their 50% DPPH inhibition concentration, 4.94 μg/mL. The results indicated this fraction exhibited greater DPPH radical scavenging activity than BHT and ascorbic acid (0.32 g dry extract/g BHT or ascorbic acid). Antibacterial activity against eight bacterial strains was assessed by disc diffusion and broth macrodilution methods. All peel extracts exhibited antibacterial activity against five pathogenic bacteria. The most sensitive strain, Staphylococcus epidermidis, was inhibited by the methanolic extract (MIC 2.0 mg/mL).     

Free radical scavenging capacity and antioxidant enzyme activity in deerberry (Vaccinium stamineum L.)

Fruit from three genotypes (‘B-76’, ‘B-59’ and ‘SHF-3A’) of deerberry [Vaccinium stamineum L.] were evaluated for fruit quality, total anthocyanin and phenolic contents, antioxidants, antioxidant capacity, and antioxidant enzyme activity. The fruit soluble solids, titratable acids, total anthocyanins, and total phenolic contents varied with genotypes. Cyanidin 3-galactoside and cyanidin 3-arabinoside were the two predominant anthocyanins. Resveratrol was also found in deerberries. Among the three genotypes, ‘B-76’ had higher amount of anthocyanins, phenolic compounds and resveratrol than ‘B-59’ and ‘SHF-3A’. Deerberries contained potent free radical scavenging activities for 2,2-Di (4-tert-octylphenyl)-1-picrylhydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS⁺), peroxyl radical (ROO), superoxide radicals (), hydrogen peroxide (H₂O₂), hydroxyl radicals (OH), and singlet oxygen (¹O₂) radicals and also had high activities of antioxidant enzymes including glutathione-peroxidase (GSH-POD), glutathione reductase (GR), superoxide dismutase (SOD), ascorbate peroxidase (AsA-POD), guaiacol peroxidase (G-POD), monodehydroascorbate radical reductase (MDAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR)] and non-enzyme antioxidants [ascorbic acid (ASA) and reduced glutathione (GSH)]. Antioxidant capacities were highly correlated to antioxidant enzymes activities. Among the three genotypes, ‘B-76’ had the highest level of antioxidants and antioxidant enzyme activity.     

Free radical scavenging activity and phenolic content in achenes and thalamus from Fragaria chiloensis ssp. chiloensis, F. vesca and F. x ananassa cv. Chandler

The total phenolic, flavonoid and anthocyanin content of achenes (true fruit) and thalamus (receptacle) from the native South American Fragaria chiloensis ssp. chiloensis (f. patagonica and f. chiloensis), Fragaria vesca and Fragaria x ananassa cv. Chandler was determined by spectrophotometric means. Highest phenolic content was found in F. vesca while lowest content was measured for white strawberry (F. chiloensis ssp. chiloensis, f. chiloensis). The total anthocyanin and total flavonoid contents in the samples investigated was lower for the white strawberry and higher in F. x ananassa cv. Chandler. Total flavonoid content showed a better correlation than total anthocyanins with the free radical scavenging effect of the extracts measured by means of the DPPH discoloration assay. In the superoxide anion assay all the acetone extracts of strawberries showed similar activity. The data presented in this study demonstrate that the amount of phenolic compounds differ significantly between species and subspecies and determine the free radical scavenging activity of fruits. On a w/w basis, higher total phenolics including flavonoids was found in achenes. The highest total anthocyanin content was found in the achenes of F. chiloensis and F. vesca, while F. ananassa presented higher antocyanin content in thalamus. The main anthocyanin in thalamus of F. ananassa (95%) were pelargonidin derivatives which were also present in F. chiloensis ssp. chiloensis f. patagonica (62.6%) but were not detected in F. vesca and F. chiloensis ssp. chiloensis f. chiloensis. In F. vesca and F. chiloensis ssp. chiloensis f. chiloensis only cyanidin derivatives were found both in thalamus and achenes.     

Antioxidant activity of Rhizoma Smilacis Glabrae extracts and its key constituent-astilbin

Rhizoma Smilacis Glabrae is widely consumed by Chinese as functional food and in folk medicine for its medicinal properties. In this study, methanol and water extracts of Rhizoma Smilacis Glabrae were prepared. The water extract was further divided into polysaccharide and supernatant fractions. Constituents in different extracts were analysed by capillary electrophoresis, and levels of total phenolics were also determined using the Folin-Ciocalteu method. Astilbin, the main constituent in the herb, was isolated and purified. Different antioxidant tests were employed to evaluate the antioxidant activities of the extracts and the isolated astilbin, and the results were compared with two commonly used synthetic antioxidants-butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Methanol, water extract and supernatant fraction showed concentration dependent antioxidant activity while polysaccharide didn’t show any antioxidant activity. Purified astilbin showed the strongest antioxidant activity in comparison to any other extracts.     

Variation of total phenolics, anthocyanins, ellagic acid and radical scavenging capacity in various raspberry (Rubus spp.) cultivars

The aim of this study was to assess the level of some phytochemicals in 19 raspberry cultivars grown in Lithuania. The content of total ellagic acid measured after 20 h acidic hydrolysis of investigated raspberry cultivars, varied from 119.8 (cv. ‘Pokusa’) to 323.5 mg/100 g (cv. ‘Bristol’). The content of total phenolics ranged from 278.6 (cv. ‘Pokusa’) to 714.7 mg/100 g (cv. ‘Bristol’). The total anthocyanins content varied from 2.1 (yellow cv. ‘Beglianka’) to 325.5 mg/100 g (black cv. ‘Bristol’). The radical scavenging capacity of the tested raspberry cultivars highly correlating with their total phenolics and total ellagic acid content (r = 0.90 and 0.92, respectively). The results of this study expand the knowledge about variation in the content of valuable bioactive compounds in raspberries and may help for the selection and validation of the most productive cultivars.     

Isolation and evaluation of the radical-scavenging activity of the antioxidants in the leaves of an edible plant, Mallotus japonicus

The antioxidative properties of a hot water extract of the leaves of Mallotus japonicus were evaluated. The extract had a high phenolic content and strong antioxidative activity, compared with green tea, rooibos tea, and red wine. Six phenolic compounds were isolated as antioxidative components by HPLC. They were identified as mallotinic acid, mallotusinic acid, corilagin, geraniin, rutin, and ellagic acid. These antioxidative compounds were subjected to DPPH radical-scavenging, superoxide radical-scavenging, and hydroxyl radical-scavenging assays, and compared with other antioxidative compounds. Four of the compounds, mallotinic acid, mallotusinic acid, corilagin and geraniin, exhibited much stronger antioxidative activity than gallic acid, rutin, ellagic acid, quercetin, and chlorogenic acid, and were as active as epigallocatechin gallate (EGCG), a strong antioxidant in green tea. Mallotus japonicus leaves are an excellent source of strong natural antioxidative materials.     

Free radical scavenging activities and bioactive substances of Jerusalem artichoke (Helianthus tuberosus L.) leaves

The total phenolic content and radical scavenging activities of Jerusalem artichoke (Helianthus tuberosus L.) leaves were investigated. Results indicated that the ethyl acetate fraction contained the highest total phenolic content (266.69 ± 2.51 mg GAE/g dry extract) accompanied with strongest free radical scavenging abilities. Following an in vitro radical scavenging activity-guide fractionation procedure, six phenolic compounds which strongly quenched free radicals were separated from ethyl acetate fraction. Among them, 3-O-caffeoylquinic acid and 1,5-dicaffeoylquinic acid played a dominant role due to their strong free radical scavenging abilities and their high contents. The content of 3-O-caffeoylquinic acid in n-butanol fraction was 74.58 ± 1.05 mg/g, while 1,5-dicaffeoylquinic acid in ethyl acetate fraction was 104.51 ± 2.86 mg/g. The results imply that the leaves of Jerusalem artichoke might be a potential source of natural antioxidants.     

Antioxidant activity of Gardenia jasminoides Ellis fruit extracts

The objective of this study was to characterise the antioxidant properties of both water and ethanol extracts from the fruit of Gardenia jasminoides Ellis (GJE). The IC₅₀ values for DPPH (1,1-diphenyl-2-picryl-hydrazyl), ABTS [2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)diammonium salt], hydroxyl and superoxide radical-scavenging activities were 0.14, 0.21, 1.08 and 1.43 mg/ml for the water-based extract, and 0.36, 0.39, 1.56 and 1.99 mg/ml for the ethanol-based extract, respectively. The extracts also showed strong reducing power, nitrite-scavenging activity, inhibition of linoleic acid oxidation, superoxide dismutase-like (SOD-like) activity and catalase activity. However, the water extract had a higher antioxidant activity than the ethanol extract. In addition, the antioxidant activities were highly correlated with the observed phenolic and flavonoid contents. Therefore, our study strongly suggests that extracts derived from the fruit of Gardenia jasminoides could be an excellent source of antioxidants as dietary supplements.