Zobayed S M A, Afreen F, Goto E, Kozai T
Department of Bioproduction Sciences, Faculty of Horticulture, Chiba University, Matsudo, Chiba 271-8510, Japan.
Ann Bot. 2006 Oct;98(4):793-804. doi: 10.1093/aob/mcl169. Epub 2006 Aug 4.
Hypericum perforatum is a perennial herbaceous plant and an extract from this plant has a significant antidepressant effect when administered to humans. The plant is characterized by its secretory glands, also known as dark glands, which are mainly visible on leaves and flowers. The current study evaluates the influence of several environmental factors and developmental stages of the plant on the accumulation and synthesis of hypericin and pseudohypericin (Hy-G), the major bioactive constituents, in H. perforatum plants.
The appearance of dark glands on different parts of the plant, under several environmental conditions, was monitored by microscopy. Hy-G concentrations were quantified by high-performance liquid chromatography.
A significant presence of dark glands accompanying the highest concentrations of Hy-G was observed in the stamen tissues more than in any other organ of H. perforatum. A linear relationship between the number of dark glands and net photosynthetic rate of the leaf and Hy-G concentration in the leaf tissue was also established. A very high concentration of Hy-G was measured in the dark-gland tissues, but in the tissues without any dark glands it was almost absent. The presence of emodin, a precursor of Hy-G, at a high concentration in the dark-gland tissues, and its absence in the surrounding tissues was also observed, suggesting that the site of biosynthesis of Hy-G is in the dark-gland cells. A significantly low concentration of Hy-G (occasionally non-detectable) was measured in the xylem sap of the stem tissues. The dark-gland tissues collected from leaves, stems or flowers contained similar concentrations of Hy-G.
The concentration of Hy-G in various organs of H. perforatum plants is dependent on the number of dark glands, their size or area, not on the location of the dark glands on the plant. The study provides the first experimental evidence that Hy-G is synthesized and accumulates in dark glands.
贯叶连翘是一种多年生草本植物，该植物提取物对人体具有显著的抗抑郁作用。这种植物的特征在于其分泌腺，也称为深色腺体，主要可见于叶片和花朵上。本研究评估了几种环境因素以及植物的发育阶段对贯叶连翘中主要生物活性成分金丝桃素和假金丝桃素（Hy-G）积累与合成的影响。
通过显微镜观察在几种环境条件下植物不同部位深色腺体的出现情况。采用高效液相色谱法定量测定Hy-G浓度。
在贯叶连翘的雄蕊组织中观察到，与最高浓度的Hy-G相伴出现的深色腺体显著多于该植物的任何其他器官。还建立了深色腺体数量与叶片净光合速率以及叶片组织中Hy-G浓度之间的线性关系。在深色腺体组织中测得的Hy-G浓度非常高，但在没有任何深色腺体的组织中几乎不存在。在深色腺体组织中还观察到高浓度的Hy-G前体大黄素，而在周围组织中则不存在，这表明Hy-G的生物合成位点位于深色腺细胞中。在茎组织的木质部汁液中测得的Hy-G浓度显著较低（偶尔无法检测到）。从叶片、茎或花朵收集的深色腺体组织中Hy-G浓度相似。
贯叶连翘植物各器官中Hy-G的浓度取决于深色腺体的数量、大小或面积，而非深色腺体在植物上的位置。该研究提供了首个实验证据，证明Hy-G在深色腺体中合成并积累。
