Effect of extraction methods on kinetic,chemical composition and antibacterial activities of Tunisian Thymus vulgaris. L. essential oil

The present study aims to compare two innovative extraction techniques: microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME) through traditional extraction techniques: hydrodistillation (HD) and steam distillation (SD) for their efficiency in the extraction of the volatile compounds from Tunisian Thymus vulgaris leaves; the kinetic, yield, composition and antibacterial activities of the essential oil were assessed in vitro. Results show that the essential oils extracted by microwaves were quantitatively (yield) similar to those obtained through the conventional methods, but qualitatively, essential oils analysed by gas chromatography–mass spectrometry (GC–MS) presented 17, 11, 11 and 8 compounds obtained through SFME, MAHD, SD and HD, respectively, mostly consisting of carvacrol (89.24–41.17%), followed by γ-terpinene (11.37–1.37%) and para-cymene (27.95–2.05%). The essential oils were screened for antibacterial activity against 5 microorganisms. All essential oils obtained by studied extraction methods showed the same resistance against Gram (?) and Gram (+) bacteria. The SFME method gave the best results: rapid kinetic of extraction (30 min vs. 35 min for MAHD, 120 min for SD, and 180 min for HD), less energy saving and cleanest process.     

Physicochemical properties,antioxidant activity and inhibition of α‐glucosidase of a novel fermented pepper (Capsiccum annuum L.) leaves‐based vinegar

The aim of this study was to utilise by‐product pepper leaves for vinegar production due to its nutritional value. Changes in physicochemical and functional properties in four main process from raw material (leaves) to lactic acid (juice), alcohol (wine) and acetic acid (vinegar) fermentations were evaluated and compared. Their nutritional compositions were significantly different and particularly the wine and vinegar had higher total phenol content and their expanded diversity than the juice and then leaves (P < 0.05). Difference in values for phenolic compound was highly correlated with their α‐glucosidase inhibitory (AGI) and antioxidant capacities in DPPH and superoxide radical scavenging and reducing power assays (r = 0.919–0.981); vinegar ≥ wine > juice > leaves. Especially, AGI activity was greatly enhanced depending on fermentation steps beyond expectation. Thus, these data confirm that pepper leaves is a good functional source and the vinegar fermentation improved the functionality in stages.     

Kinetics of Pressure Cycling Extraction of Solute from Leaves of Mate (Ilex paraguariensis) Dispersed in Water

A set of seven extraction experiments was performed to investigate the influence of pressure cycles on the kinetics of solute removal from leaves of mate dispersed in water. The mass ratio of liquid to dry solid (40), the temperature (32°C), and time of extraction (3600?s) were not varied. Five extraction runs were under cyclic pressurization (1?cycle?=?300?s at 91.4?kPa?+?300?s at 182.8?kPa) and stirring speeds (S) of 0, 150, 500, 1500, and 2000?rpm, while the two other ones were at constant pressure (182.8?kPa) and S close to 1500 and 2000?rpm. Based on seven pairs of parameters of a reliable second-order kinetic model (R²?≥?0.967), cyclic pressurization had no effect on equilibrium and kinetics of extraction (p?>?0.05) when the role of convection on solute transfer was negligible (S?≥?500?rpm). In the stirring speed range from 500 to 2000?rpm, the operation was controlled by diffusion (Bi >?1.7?×?10³), so a transient two-dimensional diffusion model was able to describe correctly the changes of solute concentration with time. Below 500?rpm, solute transfer was governed by a combination of diffusion and convection with the external resistance to mass transfer as a function of S (16?≤?Bi?≤?28).     

基于LCTF成像和ABS算法的小白菜光谱特征波段提取研究

基于液晶可调滤波器(LCTF)和CMOS组合的多光谱成像系统,在435~720nm波段范围内,以每隔5nm波段对小白菜叶片进行灰度值信息的提取,然后求出各个波段的灰度值平均值、标准差以及相关系数,并采用自适应波段选择法(ABS)提取出小白菜叶片的波段指数,最后通过波段指数的排序选取出小白菜叶片的有效特征波段。实验结果表明,用ABS的特征波段提取的算法,能够快速有效地获取小白菜叶片的光谱信息,在445nm、450nm、455nm、680nm、685nm、690nm、695nm和710nm波段具有较理想的波段指数值,有较大的光谱信息量。因此,这些波段可以很好地作为识别小白菜叶片的有效特征信息波段。     

不同采收期水冬瓜叶的主成分分析及抗炎镇痛谱效关系研究

为筛选水冬瓜叶抗炎镇痛活性成分,采用高效液相色谱(HPLC)建立不同采收期10批次水冬瓜叶药材指纹图谱,对其进行主成分分析,并基于皮尔逊相关分析法探讨不同采收期水冬瓜叶药材抗炎镇痛的谱效关系。结果显示,不同采收期水冬瓜叶药材HPLC指纹图谱中有17个共有峰,10批次药材的相似度为0.875~0.973。聚类分析将不同采收期水冬瓜叶药材分为3类。主成分分析共得到3个主成分。经皮尔逊相关分析,峰17、峰14、峰12、峰15、峰13、峰5、峰16和峰4可能为水冬瓜叶药材镇痛作用的物质基础,峰6、峰8(异槲皮苷)、峰11、峰7(金丝桃苷)、峰5、峰3、峰4、峰13、峰9和峰1可能为水冬瓜叶药材抗炎作用的物质基础。     

图像亮度信息法选取多光谱莲花白叶片特征波段

利用液晶可调谐滤波器(LCTF)和CMOS相机组合的多光谱成像系统,在波长400~720nm内以5nm为间隔对莲花白叶片进行多光谱成像。首先根据图像亮度信息法的原理,计算得到各波段莲花白叶片的可识别度;然后对莲花白叶片的可识别度进行大小排序,综合图像的信息特征和可识别度,得出555nm、715nm、710nm、575nm、535nm、520nm、720nm、605nm和650nm 9个波段有较好的识别度;最后根据欧氏距离法和光谱角度匹配法分别对莲花白叶片的特征波段的分类精度予以统计,得到两种方法的分类精度分别为95.56%和93.13%。实验证明,选取的9个波段对莲花白叶片具有较好的分类精度,可作为莲花白叶片的特征波段。     

皖南红豆杉枝叶中总黄酮抗肿瘤活性研究

以MTT法考察皖南红豆杉枝叶中总黄酮的体外抗肿瘤活性;以小鼠移植瘤模型测定总黄酮对荷瘤小鼠抑瘤率和腹腔巨噬细胞吞噬能力,研究其体内抗肿瘤活性和免疫调节作用。结果表明,总黄酮对S180细胞生长有显著抑制作用,呈现剂量依赖关系。体内试验表明,与生理盐水组相比,总黄酮对小鼠S180实体瘤有显著抑制作用（P〈0.01）,可提高荷瘤小鼠的脾指数。与环磷酰胺组相比,总黄酮可使荷S180实体瘤小鼠腹腔巨噬细胞吞噬能力显著升高（P〈0.01）,提示其对小鼠无免疫抑制作用。     

微波提取红豆杉枝叶中多糖的工艺研究

在单因素实验的基础上,采用Box-Behnken中心组合实验和响应面分析法,优化了皖南红豆杉枝叶中多糖的微波提取工艺。研究了提取时间、微波功率、料液比和浸泡时间对红豆杉枝叶多糖提取率的影响,建立了影响因素与响应值之间的数学模型,确立最佳提取工艺。结果表明:皖南红豆杉枝叶中多糖的最佳提取工艺为:微波提取6.11 min,液料比为30∶1,浸泡时间为119.21 min,微波功率为6 kW。该方法为提高皖南红豆杉枝叶中多糖成分的提取提供了基础。