| Ginkgo terpene trilactones (TTLs), ginkgolides and bilobalide, which are unique compounds in nature that occur in leaves of Ginkgo biloba L., have been used as herbal supplements for health-beneficial purposes, such as neuroprotective effects, for about forty years. The purpose of this dissertation was to investigate some of the chemical and biochemical properties of TTLs that relate to the quality and biological functions of ginkgo products.; A rapid method was developed for the quantitative analysis of the pharmacologically-active terpene trilactones, ginkgolides (G-A, G-B, G-C, and G-J) and bilobalide (BB), in Ginkgo biloba leaves and pharmaceutical ginkgo products. The method employs sequential aqueous and organic extractions followed by RP-HPLC/RI, and it substantially reduces analysis time compared to a currently-accepted reference method.; The natural accumulation of TTLs in ginkgo leaves within one vegetative season in Madison, WI, was investigated, and it was found that the amount of total TTLs in ginkgo leaves fluctuated significantly during the season with a peak accumulation occurring in August. The contents of TTLs accumulated in leaves from younger trees were higher than those from older trees, and the contents of TTLs in female trees were higher than in male trees.; Bilobalide, the most abundant component of TTLs, was exposed to a range of pH and temperature conditions using aqueous model systems. It was found that bilobalide disappearance via lactone hydrolysis was governed by pH, and it followed first order degradation kinetics. Open-ring forms rather than the closed-ring lactone form of bilobalide were found to exhibit antioxidant activity in an ABTS cation radical model system. The lactone (closed-ring) forms of ginkgolide A and B did not show antioxidant activity in the ABTS cation radical system. Prooxidant activity in a long-chain polyunsaturated fatty acid lipid peroxide assay was observed under lighted condition. In defined model systems, the various TTLs exhibited differing hydrolytic behavior and antioxidant activities.; Two in vitro cell systems, Hepa 1c1c7 and TCP-1 cells, were employed to screen selected TTLs for possible anticancer and immunoregulation activities using quinone reductase and macrophage inflammatory protein---1alpha production, respectively, as biomarkers. G-A, G-B and BB all exhibited mild anticancer and proinflammatory activities as indexed by the screening tests. Thus, TTLs might contribute anticarcinogenic and immunostimulant activities that could be useful in nutripreventative regimes. |
