Studies On The Chemical Constituents And Bioactivities Of Three Medical Plants

The thesis consists of six chapters. Chapter one presents a review on the bioactive chemical constituents of plants in family Ericaceae. The second chapter elaborates the studies on the grayanane diterpenoids from Pieris japonica. Chapters three and four deal with the isolation and determination of the chemical constituents of two plants--Breynia fruticosa and Helminthostachys zeylanica. In the fifth chapter, bioactivities of the prenylated flavonoids isolated from the Epimedium brevicornum Maxim. are reported. And the last chapter is the conclusion of the whole thesis.Sixty compounds, including eighteen new ones, were isolated from the above three specicies, and these compounds contain diterpenoids, triterpenoids, lignans, and flavonoids. The structures of the compounds were elucidated on the basis of extensive spectroscopic analysis. The new compounds are mainly diterpenoids, among them, two unique chlorinated multi-acylated3,4-seco grayanane diterpenoids, two novel6,10epoxy3,4-seco grayanane diterpenoids and a4,7epoxy3,4-seco grayanane diterpenoids were obtained. The absolute configuration of one of the chlorinated diterpenoids neopierisoid A was ditermined by X-ray diffraction. The antifeedant effect of some of the obtained diterpenoids and the antioxidant activity of flavonoids and phenolic compounds in Pieris japonica were evaluated.Pieris japonica, a well-known poisonous plant belonging to the family Ericaceae, has a rich distribution in hill and valley regions. It has been reported that livestock fall into a coma after accidental ingested of the plant. Previous chemical investigations on this plant resulted in the isolation of triterpenoids, diterpenoids, flavonoids and phenolic glycosides, while grayanane diterpenoids are the main constitutes in P. japonica. Our meticulous investigation on the chemical constituents, especially grayanane diterpenoids, from the flowers of P. japonica led to the isolation of34compounds, including13new grayanane diterpenoids and a new phenolic glycoside:neopierisoid A (1), neopierisoid B (2), neopierisoid C (3), neopierisoid D (4), neopierisoid E (5), neopierisoid F (6), neopierisoid G (7), neopierisoid H (8), neopierisoid I (9), neopierisoid J (10), neopierisoid K (11), neopierisoid L (12), neopierisoid M (13), and benzyl 2-hydroxy-4-O-β-D-glucopyranosyl-benzoate (14). The known compounds were identified as:pierisformotoxin G (15), secorhodomollolides A-B (16-17), pierisformotoxins E-F (18-19), secorhodomollolides E-H (20-23), secorhodomollolides C-D (24-25), pierisoids A-B (26-27), pierisformotoxins A-B (28-29), pierisformosins B, C (30,31),(2S,3R)-ent-catechin (32), quercetin (33),1-phenylbutane-2,3-diol (34). Most of the isolated diterpenoids are3,4-seco grayanane diterpenoids, including sixteen3,4-seco grayanane diterpenoids with the lactone group located between C-3and C-5, nine compounds with the lactone group located between C-3and C-10and two3,4-seco grayanane diterpenoids without acylated substitute. Other grayanane diterpenoids (three ones) have normal5/7/6/6skeleton. It is meaningful that among the31grayanane diterpenoids, we firstly reported two unusual defensive chlorinated diterpenoids bearing5,7,6,5ring system and12chiral center from the whole family Ericaceae. The antifeedant effect of some of the obtained diterpenoids compounds in Pieris japonica were evaluated. The results showed the unusual highly acylated chlorinated3,4-seco-grayanane diterpenoids, neopierisoids A and B, had antifeedant activity against pieris brassicae indicating the toxic properties of P. japonica might serve as a defensive role in the plant. The antioxidant activity of flavonoids and phenolic compounds in Pieris japonica were also evaluated.Breynia fruticosa (L.) Hook. f. is widely distributed in southern China and used as a Chinese folk medicine for the treatment of chronic bronchitis and inflinflammation. In addition, B. fruticosa had been used as an important ingredient of the plant medicine in the treatment of snakebite. Our further investigation of this plant collected from Xishuangbanna of Yunnan Province led to the isolation of20compounds, including2new ones:(7S,8R,7’S)-9,7’,9’-trihydroxy-3,4-methylenedioxy-3’-methoxy[7-O-4’,8-5’]neolignan (1),(7S,8R,7’S)-9,9’-dihydroxy-3,4-methylenedioxy-3’,7’-dimethoxy [7-0-4’,8-5’] neolignan (2). The18known compounds were identified as:9,9’-dihydroxy-3,4-methylenedioxy-3’-methoxy [7-0-4’,8-5’] neolignan (3),(-)-machicendiol (4), pinoresinol (5),4"-phenol group-6-O-methyl-propionyl-β-D-pyranglucoseglycoside (6), hydroquinone O-[6-(3-hydroxyisobutanoyl)]-β-galactopyranoside (7),β-D-glucopyranoside,4-hydroxyphenyl,6-(2-methylbutanoate)(8), arbutin6’-butyrate (9), arbutin (10), pyrocatechol-O-β-D-glucopyranoside (11), α/β-D-glucopyranose,6-(4-hydroxybenzoate)(12), α/β-D-glucopyranose,6-(3-phenyl-2-propenoate)(13), ursolic acid (14), apocynol A (15), naringenin (16), trans-cinnamic acid (17), cinnamic acid (18), diphenol (19),3,4-dihydroxy-cinnamic aldehyde (20). By the using of calculations of OR spectrum, together with OR and calculated ECD spectra method, we established the absolute configurations of C-7’ hydroxy group substituted neolignans for the first time. The neolignans were tested for in vitro cytotoxicity against A459,150HCT116, MCF-7and U87-MG human cancer cell lines using the MTT method. However, none of them showed obvious cytotoxicities with values of IC50>50μM, which suggested that these compounds were not the poisonous constituents in the plant.In Chinese traditional medicine, Helminthostachys zeylanica (L.) Hook., known as "Ding-Di-U-Gon", have been used for centuries in the treatment of inflammation and various hepatic disorders. The plant has been shown to exhibit anti-inflammatory, antiphlogistic, antipyretic, and hepatoprotective activities. Flavonoids with prenyl or geranyl groups have been reported to have specific bioactivities, such as cytotoxic activity, inhibitory activity and strong antioxidant effects. The flavonoids, ugonins A-L, a have been identified from H. zeylanica.The present study on the ethanolic extract of the dried whole plant of H. zeylanica collected from Xishuangbanna of Yunnan Province resulted in the isolation and characterization of a new prenylated flavonoid, neougonin A, and five known compounds:4"a,5",6",7",8",8"a-hexahydro-5,3’,4’-trihydroxy-5",5",8"a-trimethyl-4H-chromeno[2",3":7,8]flavone(2),4"a,5",6",7",8",8"a-hexahydro-5,3’,4’-trihydroxy-5",5",8"a-trimethyl-4H-chromeno[2",3":7,8]flavone (3), ugonin J (4), ugonin E (5), ugonin N (6).Epimedium brevicornu Maxim. is one of the most frequently used Chinese herbs that has been used for thousands of years in formulas prescribed for the nourishment of bone and gonadal functions. Prenyl-flavonoids were the main and characteristic components of the plant E. brevicornu and showed anti-microbial, insecticidal as well as lowering blood pressure, anti-bloodcoagulation, anti-viral, anti-osteoporosis activity. Two prenyl-flavonoids, anhydroicaritin and2"-hydroxy-3"-en-anhydro-icaritin, were isolated from the main effective fraction (CHCl3-Me2CO,7:3part) and proved, for the first time, to have the ability to promote proliferation and differentiation of murine osteoblastic MC3T3-E1cells, which suggested that both compounds have the potential to be candidates for osteogenic compounds for bone regenerative medicine.