This review will summarize some of the important reports on the chemistry and the biological activities of Dioscorea steroid saponins from the literature data of recent years (2000)(2001)(2002)(2003)(2004)(2005)(2006) and from the authors' studies. These discoveries became possible as a result of the scientific development of isolation, structure elucidation, and the development of in vitro bioassays. Over 50 steroid saponins of furostane-, spirostane-, and pregnane-type skeleton have been discovered and characterized from 13 Dioscorea species, namely, D. bulbifera L., D. cayenensis Lam.-Holl, D. colletii Hook. F. var. hypoglauca (Palib.) Pei et Ting, D. deltoidea Wall var. orbiculata, D. futschauensis R. Kunth, D. nipponica Mak., D. panthaica Prain et Burkill, D. parviflora Ting, D. polygonoides Humb. et Bonpl., D. pseudojaponica Yamamoto, D. spongiosa Xi, Mizuno et Zhao, D. villosa L., D. zingiberensisWright. The main biological and pharmacological properties of Dioscorea saponins concern cytotoxic and antifungal activity, which are highlighted.

Our previous phytochemical studies on the methanolic extract of the rhizome of Dioscorea cayenensis LAM.-HOLL led to the isolation of a new furostanol saponin.1) Further detailed investigation of the same extract has resulted in the isolation of a new furostanol glycoside (1) together with three known spirostanol saponins 2-4. Their structures were elucidated mainly by 1D and 2D NMR experiments (COSY, TOCSY, NOESY, HSQC and HMBC), and by HR-ESI-MS and FAB-MS. In addition, the antifungal activity of these compounds against three human pathogenic species of Candida is presented.The n-BuOH-soluble fraction of the MeOH-H 2 O (7 : 3) extract of the rhizome of D. cayenensis was subjected to repeated CC over silica gel to yield compounds 1-4. Compound 1, an amorphous powder, showed IR absorptions at 3371 (OH), 2929 (CH), 1736 (CO), 1680 and 1035 cm Ϫ1 . The high-resolution ESI mass spectrometry (HR-ESI-MS) (positive-ion mode) of 1 exhibited a pseudomolecular ion peak at m/z 1231.5697 [MϩNa] ϩ (Calcd 1231.5724), consistent with a molecular formula of C 57 H 92 O 27 Na. Its negativeion FAB-MS showed a quasimolecular ion peak at m/z 1207, indicating a molecular weight of 1208. Acid hydrolysis of 1 yielded glucose, rhamnose (TLC) and an aglycone which was identified as a furostanol-type steroid by comparison of the NMR data of 1 (Table 1) with those of known spirostane-type steroids.1-3) The comparison of NMR data of 1 with literature data allowed the identification of the aglycone as the previously reported (3b,25R)-20,22-seco-25-furost-5-en-20,22-dione-3,26-diol (aglycone of dioscoreside D), 2,3) and the five sugar residues as two b-glucopyranosyl (Glc) and three a-rhamnopyranosyl (Rha) moieties. The absolute configurations of glucose and rhamnose were determined to be D and L, respectively, by GC analysis of chiral derivatives of the sugars in the acid hydrolysate (see experimental section). The between Rha H-1 (dϭ6.10) and Glc I C-2 (dϭ78.0), Rha II H-1 (dϭ5.58) and Glc I C-4 (dϭ77.9) and Rha III H-1 (dϭ6.03) and Rha II C-4 (dϭ79.8).

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The influence of temperature (T) and water activity (aw) on the growth rate (mu) of seven moulds (Alternaria alternata, Aspergillus flavus, Cladosporium cladosporioides, Mucor racemosus, Penicillium chrysogenum, Rhizopus oryzae and Trichoderma harzianum) was assessed in suboptimal conditions. Firstly, the dependence of fungal growth on temperature, at aw 0.99, was modelled through an approach described previously for bacteria. A dimensionless growth rate variable: mu(dimalpha)=mu/mu (optalpha) depended on the following normalised temperature: T(dim)=(T-T(min))/(T(opt)- T(min)) according to a power function: mu(dimalpha)=[T(dim)]alpha, where alpha was an exponent to be estimated. Secondly, the same approach was used to describe the influence of aw on fungal growth, at the respective optimum temperatures for each mould. Similarly, mu(dimbeta)=mu/mu(optbeta) depended on the following normalised water activity: a(wdim)=(aw-a(wmin))/(a(wopt)-a(wmin)) according to a power function: mu(dimbeta)=[a(wdim)](beta). Results show: (i) for each mould, the alpha-value is significantly less than the beta-value, confirming that water activity has a greater influence than temperature on fungal development; (ii) the alpha-values and the beta-values depend on the mould; (iii) the alpha-value is less than 1 for the mesophilic mould A. flavus, whereas the other moulds are characterised by higher alpha-values ranging from 1.10 to 1.54; (iv) the mesophilic A. flavus exhibits a low beta-value, 1.50, compared to the hydrophilic T. harzianum, beta=2.44, while beta-values are within the range (1.71-2.37) for the other moulds.

Aims: The influence of temperature, water activity and pH on the growth of Aeromonas hydrophila, and on its survival after transfer in nutrient-poor water were assessed. Methods and Results: Experiments were carried out according to a Box-Behnken matrix at 10-30°C, 0AE95-0AE99 water activity (a w ) and pH 5-9. The effect of each factor on the kinetic parameters of growth (i.e. the maximal specific growth rate, l max , and the lag time, k) and on the decline of the bacteria in microcosm water (time to obtain a reduction of 5 log, T 5 log ) were studied by applying central composite design. Conclusions: The major effect of temperature and water activity on the growth of A. hydrophila was highlighted, whereas the effect of pH in these experimental conditions was not significant. Models describing the effect of environmental parameters on the growth of A. hydrophila were proposed. The effect of the growth environment, and particularly the incubation temperature, have an influence on the survival ability of the bacteria in nutrient-poor water. Significance and Impact of the Study: The Box-Behnken design was well suited to determine the influence of environmental factors on the growth of A. hydrophila and to investigate the effect of previous growth conditions on its survival in microcosm water.

Three new steroidal saponins (1-3) were isolated from the roots of Smilax medica, together with the known disporoside A (4). The structures of the new compounds were elucidated mainly by extensive spectroscopic analysis (1D and 2D NMR, FABMS, and HRESIMS). Compounds 1, 2, and 4 demonstrated weak antifungal activity against the human pathogenic yeasts Candida albicans, C. glabrata, and C.tropicalis, with MIC values between 12.5 and 50 microg/mL.