In this study, responses of rice under drought stress correlating with changes in chemical compositions were examined. Among 20 studied rice cultivars, Q8 was the most tolerant, whereas Q2 was the most susceptible to drought. Total phenols, total flavonoids, and antioxidant activities, and their accumulation in water deficit conditions were proportional to drought resistance levels of rice. In detail, total phenols and total flavonoids in Q8 (65.3 mg gallic acid equivalent (GAE) and 37.8 mg rutin equivalent (RE) were significantly higher than Q2 (33.9 mg GAE/g and 27.4 mg RE/g, respectively) in both control and drought stress groups. Similarly, the antioxidant activities including DPPH radical scavenging, β-carotene bleaching, and lipid peroxidation inhibition in Q8 were also higher than in Q2, and markedly increased in drought stress. In general, contents of individual phenolic acids in Q8 were higher than Q2, and they were significantly increased in drought stress to much greater extents than in Q2. However, p-hydroxybenzoic acid was found uniquely in Q8 cultivars. In addition, only vanillic acid was found in water deficit stress in both drought resistant and susceptible rice, suggesting that this phenolic acid, together with p-hydroxybenzoic acid, may play a key role in drought-tolerance mechanisms of rice. The use of vanillic acid and p-hyroxybenzoic acid, and their derivatives, may be useful to protect rice production against water shortage stress.

Celastrus hindsii is a popular medicinal plant in Vietnam and Southeast Asian countries as well as in South America. In this study, an amount of 12.05 g of an α-amyrin and β-amyrin mixture was isolated from C. hindsii (10.75 g/kg dry weight) by column chromatography applying different solvent systems to obtain maximum efficiency. α-Amyrin and β-amyrin were then confirmed by gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS), and nuclear magnetic resonance (NMR). The antioxidant activities of the α-amyrin and β-amyrin mixture were determined via 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,20-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays with IC₅₀ of 125.55 and 155.28 µg/mL, respectively. The mixture exhibited a high potential for preventing gout by inhibiting a relevant key enzyme, xanthine oxidase (XO) (IC₅₀ = 258.22 µg/mL). Additionally, an important enzyme in skin hyperpigmentation, tyrosinase, was suppressed by the α-amyrin and β-amyrin mixture (IC₅₀ = 178.85 µg/mL). This study showed that C. hindsii is an abundant source for the isolation of α-amyrin and β-amyrin. Furthermore, this was the first study indicating that α-amyrin and β-amyrin mixture are promising in future therapies for gout and skin hyperpigmentation.

In this study, different plant parts (barks, flowers, inner skins, kernels and leaves) of Castanea crenata (Japanese chestnut) were analyzed for total phenolic, flavonoid, and tannin contents. Antioxidant properties were evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), reducing power, and β-carotene bleaching methods. The highest total phenolic and tannin contents were found in the inner skins (1034 ± 7.21 mg gallic acid equivalent/g extract and 253.89 ± 5.59 mg catechin equivalent/g extract, respectively). The maximum total flavonoid content was observed in the flowers (147.41 ± 1.61 mg rutin equivalent/g extract). The inner skins showed the strongest antioxidant activities in all evaluated assays. Thirteen phenolic acids and eight flavonoids were detected and quantified for the first time. Major phenolic acids were gallic, ellagic, sinapic, and p-coumaric acids, while the principal flavonoids were myricetin and isoquercitrin. The inner skin extract was further fractionated by column chromatography to yield four fractions, of which fraction F3 exhibited the most remarkable DPPH scavenging capacity. These results suggest that C. crenata provides promising antioxidant capacities, and is a potential natural preservative agent in food and pharmaceutical industries.

Phalaenopsis spp. is the most commercially and economically important orchid, but their plant parts are often left unused, which has caused environmental problems. To date, reports on phytochemical analyses were most available on endangered and medicinal orchids. The present study was conducted to determine the total phenolics, total flavonoids, and antioxidant activity of ethanol extracts prepared from leaves and roots of six commercial hybrid Phalaenopsis spp. Leaf extracts of “Chian Xen Queen” contained the highest total phenolics with a value of 11.52 ± 0.43 mg gallic acid equivalent per g dry weight and the highest total flavonoids (4.98 ± 0.27 mg rutin equivalent per g dry weight). The antioxidant activity of root extracts evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging assay and β-carotene bleaching method was higher than those of the leaf extracts. Eleven phenolic compounds were identified, namely, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, vanillin, ferulic acid, sinapic acid, p-coumaric acid, benzoic acid, and ellagic acid. Ferulic, p-coumaric and sinapic acids were concentrated largely in the roots. The results suggested that the root extracts from hybrid Phalaenopsis spp. could be a potential source of natural antioxidants. This study also helps to reduce the amount of this orchid waste in industrial production, as its roots can be exploited for pharmaceutical purposes.

Background: Clausena indica fruit is commonly used for food ingredients and traditional medicines in tropical countries, however, information about its biological activities and chemical profiles has been inadequately reported. Methods: In this study, a bio-guided fractionation of antioxidants and α-amylase inhibitors from hexane (MH) and ethyl acetate (ME) extracts of C. indica fruit (pericarp and seed) was carried out. Eleven fractions from MH (D1–D11) and 17 fractions from ME (T1–T17) were obtained from column chromatography over silica gel, which were then examined for anti-radical capacity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, and pancreatic α-amylase inhibition, a key enzyme linked to type 2 diabetes. Results: Of isolated fractions, the fraction T4 revealed the most potent anti-DPPH activity (IC50 = 0.13 mg/mL), whereas T2 exhibits the strongest ABTS cation scavenging ability (IC50 = 0.31 mg/mL). In the enzymatic assay, the fractions D3 and T4 significantly inhibit the α-amylase reaction with IC50 values of 0.34 and 0.86 mg/mL, respectively. Remarkably, α-amylase suppression of T4 is close to acarbose and over four times stronger than palmitic acid, which are the well-known α-amylase inhibitors (IC50 = 0.07 and 1.52 mg/mL, respectively). The active constituents from fractions were identified by gas chromatography-mass spectrometry (GC-MS). The results show that the fraction D3 contains five major compounds, which are grouped in five classes consisting of fatty acids, phenols, benzodioxoles, alcohols, and sesquiterpenes. Among them, palmitic acid is the most dominant compound (32.64%), followed by 2R-acetoxymethyl-1,3,3-trimethyl-4t-(3-methyl-2-buten-1-yl)-1t-cyclohexanol (16.69%). Whilst, six major compounds belonging to fatty acid and coumarin classes are identified in the fraction T4. The most abundant compound in T4 is dentatin (47.32%), followed by palmitic acid (15.11%). Conclusions: This is the first finding that C. indica fruit can be a promising source for the development of natural antioxidant and antidiabetic agents. Additionally, the outcome reveals that dentatin, a known natural antineoplastic agent, can be feasibly exploited from C. indica fruit.