扁担木叶片和次生木质部解剖和水分生理特征的可塑性

基于叶片和次生木质部解剖特征及水分生理指标观测,研究了淮北相山不同群落中扁担木的表型可塑性.结果表明,扁担木叶片结构表现出中生特点：叶为异面叶,较薄,角质层不甚发达,气孔密度较小.次生木质部表现出旱生特点：导管频率和复孔率较高,导管分子短而窄,纤维很短,射线很低.扁担木叶片、次生木质部的解剖和水分生理特征均表现出一定的可塑性,其可塑性指数高低顺序为次生木质部解剖特征（0.24）＞水分生理特征（0.19）＞叶片解剖特征（0.18）.与侧柏林和混交林相比,灌丛中扁担木个体对干旱生境有一定的适应能力,表现在次生木质部导管分子短,导管频率高,单孔率低,木纤维短,射线矮小,具有较大的相对输导率和较小的脆性指数;叶片水势、组织含水量、自由水含量较低,叶面积、比叶面积较小,而束缚水含量、束缚水自由水比值较高.扁担木的解剖和生理可塑性,使之能忍受群落演替早期的干旱生境,更好地适应演替后期的中生环境,从而成为广布种和混交林中的优势种.     

Quick Identification of Piperidine Alkaloid from Roots of Grewia nervosa and Their Glucosidase Inhibitory Activity

Grewia nervosa is a herbal plant used in traditional medicine for different purposes. Bioassay‐guided chemical fractionation of G. nervosa roots resulted in an identification of two known and one new compound, namely microgrewiapine A, homomicrogrewiapine, and N‐methylmicrocosamine, respectively. Their structures were determined using combination of LC/HR‐MS, ¹H‐NMR, and IR spectral analyses and followed by comparison with those reported in the literature. The problematic separation of these alkaloids on traditional column chromatography (Silica gel, Octadecyl silane, Sephadex) was resolved by using HPLC. Structurally similar compounds from the piperidine family have been characterized by using HR‐MS analysis in combination with NMR data of crude samples. The major constituent i.e. N‐methylmicrocosamine isolated from the butanol fraction of methanol root extract (MRE) was found to possess the dose dependent α‐glucosidase inhibition activity with an IC₅₀ value of 53.40 μm . Furthermore, N‐methylmicrocosamine showed maximum α‐glucosidase inhibition of 97.48 ± 0.7% at 107.5 μm , which is approximately 1.3 × 10³ fold higher than the activity shown by acarbose (97.72% inhibition at 61.95 mm ), a standard anti‐diabetic drug available commercially. This work also reports the in vitro α‐glucosidase inhibitory activity of the major alkaloids isolated from G. nervosa for the first time.