Phytochemical constituents from dietary plant Citrus hystrix

Chemical investigation of the fruit peel of dietary plant Citrus hystrix offered two new flavones 5,6,4′-trihydroxypyranoflavone I and 5,4′-dimethyl-6-prenylpyranoflavone XIII besides 11 known compounds. The structures of all compounds were elucidated with the aid of suitable analytical methods like 1D, 2D-NMR, mass and single crystal X-ray analysis. An X-ray crystal study of compound II was done for the first time and the compounds I–VI, XI and XII are hitherto not reported from this plant. Biological studies revealed that compound I found to have a good antidiabetic and antiacetylcholinesterase activities meanwhile compounds II, III and V showed a significant free radical scavenging ability as well as antioxidant capacity. In addition, compounds I, IV, V and VI showed cytotoxicity against U87, A549 and MCF-7 cells. Overall, the new compound I showed valuable bioactive properties. Due to insufficient quantity of compound XIII, biological studies were not done.     

Generic leaves

A remarkable theorem of E. Ghys asserts that, for any harmonic measure on a compact, foliated metric space, -almost every leaf has 0, 1, 2 or a Cantor set of ends. In this paper, analogous results are proven for topologically almost all (i.e., residual families of) leaves. More precisely, if some leaf is totally recurrent, a residual family of leaves is totally recurrent with 1, 2 or a Cantor set of ends. A "local" version of this theorem asserts that, in general, topologically almost all leaves have 0, 1, 2 or a Cantor set of dense ends. Received: October 1, 1997     

Validated reversed phase LC method for quantitative analysis of polymethoxyflavones in citrus peel extracts

Polymethoxyflavones (PMFs), which exist exclusively in the citrus genus, have biological activities including anti-inflammatory, anticarcinogenic, and antiatherogenic properties. A validated RPLC method was developed for quantitative analysis of six major PMFs, namely nobiletin, tangeretin, sinensetin, 5,6,7,4'-tetramethoxyflavone, 3,5,6,7,3',4'-hexamethoxyflavone, and 3,5,6,7,8,3',4'-heptamethoxyflavone. The polar embedded LC stationary phase was able to fully resolve the six analogues. The developed method was fully validated in terms of linearity, accuracy, precision, sensitivity, and system suitability. The LOD of the method was calculated as 0.15 microg/mL and the recovery rate was between 97.0 and 105.1%. This analytical method was successfully applied to quantify the individual PMFs in four commercially available citrus peel extracts (CPEs). Each extract shows significant difference in the PMF composition and concentration. This method may provide a simple, rapid, and reliable tool to help reveal the correlation between the bioactivity of the PMF extracts and the individual PMF content.     

Microencapsulation of cinnamon leaf (Cinnamomum zeylanicum) and garlic (Allium sativum) oils in β-cyclodextrin

Cinnamon leaf (CLO) and garlic oils (GO) are good antimicrobials, however, their volatility complicates their application as food preservatives. Hence, microencapsulation of CLO and GO with β-cyclodextrin (β-CD) was studied at 4:96, 8:92, 12:88, and 16:84 (oil:β-CD) percent weight ratios. Microcapsule characterization included gas chromatography analysis, moisture sorption–desorption isotherms, infrared spectroscopy (IR), and antifungal activity against Alternaria alternata. Major oil constituents were eugenol for CLO and allyl disulfide for GO. The 16:84 ratio (CLO:β-CD) showed the highest eugenol content; the allyl disulfide content was higher, but not significantly different (P > 0.05) for the 12:88 and 16:84 ratios. Microcapsules showed lower moisture sorption than β-CD, although during water desorption there were no difference between them. Hydrogen bonds were detected between oil constituents and β-CD by IR spectroscopy. CLO:β-CD and GO:β-CD microcapsules displayed good antifungal activity against Alternaria alternata. Therefore, CLO and GO microcapsules can have important applications in the food industry as stable natural antimicrobial compound systems.     

High-performance liquid chromatography micro-fraction bioactive evaluation combined with countercurrent chromatographic separation of antioxidants from Citrus peel and their tyrosinase inhibition activities

In the present study, high-performance liquid chromatography micro-fraction bioactive evaluation and high speed countercurrent chromatography were performed on screening, identification and isolation of antioxidants from Citrus peel. Three compounds were screened as antioxidants and tyrosinase inhibitors using 2,2′-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation scavenging assay and tyrosinase activity test, then they were identified as eriocitrin, narirutin and hesperidin. Moreover, the solvent system ethyl acetate-n-butanol-water (6:4:10, v/v/v) was used for separation of ethyl acetate extract of Citrus peel by high speed countercurrent chromatography. In total, 0.45 mg of eriocitrin with 87.10% purity, 2.04 mg of narirutin with 95.19% purity and 1.35 mg of hesperidin with 95.19% purity were obtained from 20 mg of ethyl acetate extract of Citrus peel in a single run and then each component was subjected to 2,2′-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation scavenging assay and tyrosinase inhibition assay. Eriocitrin showed great antioxidant activity (the half-maximum concentration: 3.65 µM) and tyrosinase inhibition activity (the half-maximum concentration: 115.67 µM), while narirutin and hesperidin exhibited moderate activity. Tyrosinase inhibition activity for eriocitrin in vitro was reported for the first time. Furthermore, molecular docking between eriocitrin and mushroom tyrosinase was also studied.     

Matrix solid-phase dispersion combined with micro-fractionation bioactivity evaluation screening polymethoxylated flavones from Citrus peels

Polymethoxyflavones were a unique class of natural and safe flavonoids containing two or more methoxy groups, which were also the most abundant edible part in Citrus peel. The optimum condition in the process of selective extraction of polymethoxylated flavones from Citrus peel by matrix solid-phase dispersion (MSPD) was as follows: SBA-15 as adsorbent, ethyl acetate as eluent, the mass ratio of adsorbent to sample 1:1, and the mixture of sample and adsorbent was ground for 3 min. Twelve antioxidants were successfully screened by micro-fractionation bioactivity evaluation assay, in which four of them were flavonoid glycosides, seven of them were polymethoxylated flavones, and one was phenylpropanoid. 1-sinapoly-β-D-glucopyranoside (1) was reported for the first time in Citrus peel. And antioxidant capacity of 1-sinapoly-β-D-glucopyranoside, 5, 7, 8, 3′, 4′, 5′-hexamethoxyflavone (6), hexamethoxyflavone (11), and 5, 6, 7, 4′-tetramethoxyflavone (7) were reported for the first time. Nobiletin (compound 8), 3, 5, 6, 7, 8, 3′, 4′-heptamethoxyflavone (9) and tangeretin (10) were isolated and purified by countercurrent chromatography combined with preparative liquid chromatography. Antioxidant activity evaluation indicated that the three isolated polymethoxylated flavones owned similar antioxidant activity. This study indicated that MSPD combined with micro-fractionation bioactive evaluation was efficient in screening bioactive compounds for rapid extraction and effective pinpointing bioactive substances in natural products.     

柑橘果肉果胶的流变和结构特性

以柑橘果肉为原料,采用稀酸提醇沉法提取果胶粗品,研究了果胶溶液的浓度及热处理温度对果胶溶液流变学性质的影响.采用DEAE Cellulose-52柱对柑橘果肉粗品进行洗脱得到3个多糖组分(P-0,P-1和P-2),对其分子量、半乳糖醛酸、单糖组成及酯化度等进行分析,并利用红外光谱及核磁共振氢谱等对各组分进行结构特性分析.结果表明,柑橘果肉果胶为典型的剪切稀化型非牛顿流体;P-0,P-1和P-2组分分子量存在显著差异;柑橘果肉果胶为富含糖醛酸的酸性多糖,且是发生部分乙酰化的低酯果胶,其单糖组成以半乳糖醛酸、半乳糖、阿拉伯糖、鼠李糖和岩藻糖居多,且均以Ⅰ型聚鼠李半乳糖醛酸(RG-Ⅰ型)结构为主;3种组分糖环类型均是吡喃糖,糖苷键既有α型,又有β型.     

Selective recovery of rosmarinic and carnosic acids from rosemary leaves under ultrasound- and microwave-assisted extraction procedures

Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) are currently amongst the foremost green techniques for accelerating extraction processes. Several methods for the efficient recovery of the phenolic compounds from rosemary leaves have so far been proposed, but little data are available on the use of UAE and MAE. The aim of this work is to investigate the efficiency and selectivity of these techniques in recovering fractions of specific phenolic compounds from dried rosemary leaves using solvents that are suitable for food applications. UAE has been carried out by means of a probe system equipped with a titanium horn working at 19.5 kHz (140 W). MAE has been performed in a closed multimode reactor under N₂ (20 bar) at 100 °C. All obtained extracts were dissolved in a defined solvent volume and the solutions were directly analyzed using a combination of the HPLC-DAD-MS and TOF techniques. MAE and UAE in ethanol and acetone dramatically increased phenol yield (more than three times) as compared to more traditional solid–liquid extraction processes. In terms of selectivity, remarkably high rosmarinic acid content (6.8% of the dried extract) was obtained in ethanol under ultrasound (US). Even more impressive is the selectivity of UAE in n-hexane which gave the highest carnosic acid content, up to 13% of the dried extract. In conclusion, non-conventional energy sources and, in particular, high-intensity US have proven themselves to be rapid, efficient, and selective techniques for rosemary leaf extraction and provide fractions with high rosmarinic and carnosic acid contents.     

莲(Nelumbo nucifera)叶片结构的光镜和扫描电镜的观察

本文报道了莲的浮叶和立叶两种不同生态型叶的表面特征及解剖结构。莲的气孔器主要分布在上表皮,下表皮的则为零星分布。莲的气孔器类型多,表面结构复杂,有形态相近的六种类型,但孔口普遍呈开放状态。集中在莲鼻位置及散生在叶缘的排水器,其水孔形状与气孔器的孔口极为类似,彼     

Naturally Available Flavonoid Aglycones as Potential Antiviral Drug Candidates against SARS-CoV-2

Flavonoids are important secondary plant metabolites that have been studied for a long time for their therapeutic potential in inflammatory diseases because of their cytokine-modulatory effects. Five flavonoid aglycones were isolated and identified from the hydrolyzed aqueous methanol extracts of Anastatica hierochuntica L., Citrus reticulata Blanco, and Kickxia aegyptiaca (L.) Nabelek. They were identified as taxifolin (1), pectolinarigenin (2), tangeretin (3), gardenin B (4), and hispidulin (5). These structures were elucidated based on chromatographic and spectral analysis. In this study, molecular docking studies were carried out for the isolated and identified compounds against SARS-CoV-2 main protease (Mpro) compared to the co-crystallized inhibitor of SARS-CoV-2 Mpro (α-ketoamide inhibitor (KI), IC₅₀ = 66.72 µg/mL) as a reference standard. Moreover, in vitro screening against SARS-CoV-2 was evaluated. Compounds 2 and 3 showed the highest virus inhibition with IC₅₀ 12.4 and 2.5 µg/mL, respectively. Our findings recommend further advanced in vitro and in vivo studies of the examined isolated flavonoids, especially pectolinarigenin (2), tangeretin (3), and gardenin B (4), either alone or in combination with each other to identify a promising lead to target SARS-CoV-2 effectively. This is the first report of the activity of these compounds against SARS-CoV-2.