Comparative And The Correlative Studies On The Structure And The Content Of Anthraquinones In Aloe Leaves

Comparative and the Correlative Studies on the Structureand the Content of Anthraquinoncs in AIoe LeavesBy f Shen ZonggenSupervisor: Pro f Hu Zheng-haiInstitute of Botany, NorthWst University Xi'an 710069, PR.ChinaSuPervisor f Pro f YtZchak GuttermanBen-Gurion University of the Negev, Unit for Ecophysiology and Introductionof Desert Plans, Wyler DepartInent of Drylands AgricultUre, Jacob BlauSteinInstit'Ute for Desert Research, Sede Boker Campus, 84990, IsraelAbstractThe AlOe comPtises a large genus of over 300 species, to which additionsare regUlar being made. The genus is native to Affica, from the CaPe and thedeserts of South Affica to the tropical pats of Affica, and to the southemparts of AIabian Peninsula. Because of the widespread use of Aloe speciessince ancient times as both drugs (their phannaceutical activity anthraquinonesand their derivative) and cosmetics, Aloe plants have spread in cultivationthroughout the world. However, little information is available as to therelationships betWeen chemicals and the leaf smictures within the grouPs.In this study, we systematically investigated the structural differences, thedifferent content of mainly anthraquinones in leaves of different ages and leafparts and the correlation betWeen the smicture and the content of fOurmetabolites, barbaloin, homonataloin, Aloenin and and isomers of Aloeresin, inl0 Aloe species. We used the multiple aPProaches - anatomical, phytochemistryfluorescent, ligh and scanning electron microscopes and histochemistrymethods. The morphogenesis, histochemial location and ultfa-struCture of thestructures for production and accumulation of these metabolites were alsocarried out.The anatomical results revealed that the smicthel feamres of AlOe leavesare similar Aloe leaves usually consist of epidermis, chlorenchyma andvascular bundles. The 1eaf surface is covered by a layer of ePidermal cells thatare covered by a thick cllticle. Many sunken stomata are uniformly distributedin the ePidermis. Mesophyll can be divided into chlorenchyma and aquiferous4tissues. IdioblastS are usually distributed axnong chlorenchymatous cells.Vascular bundles, which are composed of one layer ofparenchymatus cells as asheath, phloem and Xylem tissues, are located betWeen the chlorenchyma andaquiferous tissues. There are several well-developed large parenchymatouscells, i.e. aloin cells, at the phloem pole of each bundle. The aloin cells occupythe most of the area of the cross section of a bundle. Aquiferous tissue iscomPosed of many large cells, which is full of mucilage and water, and willoccuPy 70-80% of a leaf cross-section.The results from comPndive studies indicated that there are somedifferences in leaf structutes among the different species of AlOe plants. Thethickness of epidermis in A. cameronii is about l00 pm, but in A. mutabilis andA. vera L. var chinensis it is only about 25 pm. The different pattems of thecuticle were also Observed. In general, four guard cells surround the each stoma,however, five cells toes were firstly rePorted. In addition, the thicbess ofchlorenchyma and the degree of differentiation of the chlorenchyma are alsodifferent among l0 plans tested. Most of the plants did not differentiate intopalisade and spongy tissues. In A. arborescens, the chlorenchyma can bedivided into tWo parts, palisade and isodiametfic cells. It was rePorted that thecrystals in idioblasts are mainly needle-shaPed that vary in length. However,we first observed there are no needle crystals in A. arborescens bllt 300-500pm long single column crystals in A. cmptDPada. Instead of one ring ofvascular bundles, we fOund that there are tWo rings of bundles in the basal partsof A. vera L. var chlbensltr leaves. The above smictUral differences are the newdata fOr classification of Aloe.TLC analysis demonstrated that four secondmp metabolites are mainlycontained in 9 AlOe plants, they are barbaloin, hom...