Studies On Anatomy, Histochemistry And Accumulation Of Flavonoids In Houttuynia Cordata

Houttuynia cordata Thunb. (Saururaceae) is a native perennialherbaceous plant in the eastern and southern regions of Asian. It traditionally used as atherapeutic plant, shown anti-oxidant and anti-cancer activities, and also a specialpotherb in folk purpose. And it now had been confirmed both leechdom and food asby national board of health.The dry aerial organs or fresh grass were officinal parts.The mainly biological activity components are mainly aldehyde and ketone-compounds and flavonoids, such as decanoyl acetaldehyde, Lauric aldehyde,Methyl-n- nonylketone and quercitin. In this study, we systematically investigated thedevelopment and structure of stem and leaf, the structures, components and functionsof secretory tissues, and the dynamic changes of total flavone and quercitin contentswere studied from different organs, different months and different elicitorsinducement, by using anatomy, histochemistry and phytochemistry methods.1. H. cordata Thunb. is a perennial herbaceous plant, whose shem obviouslycompartmentalize subterraneous and aerial stems. The development and primarystructure of stem is the same to other dicotyledons, the three development phasesconsist of promeristem, primary meristem and primary structure. Besides, there aresub-epidermis, perivascular fiberring and endoderm differentiation in cortex. Thestructure of subterraneous stem is the same with aerial stem, but there are different inquantity. This is the reason of their different circumstances and physiological roles,namely, aerial stem took the role in transport, sustain and photosynthesis, whilesubterraneous stem mainly took the role in storage, transport and reproduce. 2. Oil cells are single and isolated, and situate in the epidermal layer of all organs.Gland dots recorded by Chinese Pharmacopoeia in leaves were virtually oil cells.While type A, B and C secretory cells were distributed in H. cordata, and thedevelopmental patterns of all three types of cells are the same, the differences betweenthree types of secretory cells lie in their distribution, size and ontogenesis. Thedevelopmental processes of secretory cells are similar to the earlier process of oil cells,but their origin and latter development are different. Both the oil cell and glandularhair initiate from protoderm, but there are differences in their development.3. The present histochemical results indicate that the secretory tissues in H. cordataproduce diverse secondary metabolites, including flavonoids, alkaloids, phenoliccompounds, tannins, lipids, pectic-like substances, terpenoids, and aldehyde andketone-compound. Their characteristics are as follows: (a) Different secretory tissues(oil cells, secretory cells and glandular hairs) produce the same secretions, such asflavonoids, phenolic compounds, tannins, lipids and aldehyde and ketone-compound.(b) There are different secretions in the same secretory tissues. Oil cells in leavescontain pectic-like substances, which are absent in oil cells of stems; secretory cells inaerial stems contain alkaloids, which are absent in secretory cells of subterraneousstems and leaves. (c) Secretions of the three types of secretory cells are the same inthe same organ. (d) Both the aerial and hypogeal organs are involved in theproduction of secondary metabolites, such as flavonoids, phenolic compounds,tannins, lipids, terpenoids, aldehyde and ketone-compound. So the hypogeal organmay also be officinal part, which has not been stated in Chinese Pharmacopoeia(2005). (e) The active constituents in the essential oil--decanoyl acetaldehyde, Lauricaldehyde and Methyl-n-nonylketone--are accumulated in oil cells, secretory cells andglandular hairs.4. According to the biological characteristics of secretory tissues in H. cordata andits secondary metabolites, we presume the roles of these secretory tissues as chemicaldefense, physical defense, attracting pollinators, and transportation.5. As a core component of paleoherbs, H. cordata is very important for studying theorigin and early ontogenesis of secretory tissues, oil cells are derived evolutionarily from similar hairs. Oil cells and secretory cells are homogenous, or that secretory cellsmay come from oil cells. Oil cells and the secretory cells are intermediates betweenprimitive surface glandular and secretory cavities or canals during the evolution ofsecretory structures.6. Great discrepancies about the contents of total flavone and quercitin exist in eachorgan of H. cordata Thunb.. The content of total flavone in each organ shows asfollows: Leaf>fruit>flower>frond>aerial stem>subterraneous stem, The contentof quercitin in each organ appears that flower is the highest, the second is leaf, fruitand frond, the aerial stem is the lowest; The amount of total flavone and quercitin inHouttuynia cordata Thunb is increasing from July to September, and it could reachthe highest in September; The contents of both appear comparability in differentorgans or different seasons. Besides, the content of quercitin in fresh is higher than thedry plant.7. Sencondary product regulated by different elicitors is an important mediatingway in enhancing secondary product in plant cells, seeding induced by differentconcentrations of salicylic acid and methyl jasmonate accumulated higher amount ofquercitin in Houttuynia cordata to some extent. Low concentration of salicylic(50μg/ml) and high concentration of methyl jasmonate (20μg/ml) have inducedquercitin increase obvious in the seedings, from long-term effect. And mechanicaldamage can also result in great discrepancies in quercitin between control group andtreatment group.8. Young frond of Houttuynia cordata induced by UV-B irradiation to increasequercitin, and the content obviously increased after continuous irradiation for eightdays and four hours for each day. At this point, great changes happened inmorphology structures, physiology and biochemistry characters, which can beexplained that these changes are self-protection and adaption for themselves to UV-Bradiation.