O(3)-(2-Acetylamino-2-deoxy-β-d-glucopyranosyl)-oleanolic acid,a novel triterpenoid glycoside from two Pithecellobium species

A new triterpenoid glycoside containing an amino sugar moiety has been isolated from Pithecellobium cubense and P. arboreum and identified as O(3)- (2-acetylamino-2-deoxy-β-d-glucopyranosyl)oleanolic acid. β-d-Glucopyranosyl-α-spinasterol was also obtained from P. cubense.     

Properties of acyl hydrolase enzymes from Phaseolus multiflorus leaves

The properties of acyl hydrolase enzymes purified from the leaves of Phaseolus multiflorus have been studied. Hydrolase I which deacylates phosphatidylcholine and oleoylglycerol had a pH optimum towards phosphatidylcholine of 5.3. Hydrolase II which deacylates glycosylglycerides and oleoylglycerol showed pH optima of 7.3 (monogalactosyldiglyceride, MGDG) and 4.3 (sulphoquinovosyldiglyceride, SQDG). Both enzymes showed activity peaks towards oleoylglycerol at pH 6.8 and 8.8. Unesterified fatty acids and Triton X-100 inhibited the rate of SQDG hydrolysis while bovine serum albumin increased activity. An apparent K_m for SQDG of 0.15 mM was found. Hydrolase II catalysed transmethylation of liberated fatty acids during the hydrolysis of oleoylglycerol when methanol was included in the assay system. A number of salts inhibited SQDG hydrolysis but their effect on oleoylglycerol was less consistent. The position of ester cleavage of oleoylglycerol was determined by the use of H₂¹⁸O. Cell-free extracts from P. multiflorus leaves degraded SQDG as far as sulphoquinovose.     

Neue,abgewandelte pseudoguajanolide aus Psilostrophe villosa

Investigation of the North American species Psilostrophe villosa afforded, in addition to known compounds, five new sesquiterpene lactones, which all turn out to be modified pseudoguaianolides, most of them closely related to hymenolide. However, one of the lactones is a new type of nor-pseudoguaianolide. Furthermore a new monoacetylated borneol-β-D-glucoside is present. The chemotaxonomic situation is discussed briefly.     

Acacipetalin in Acacia constricta from north America

Acacipetalin, previously known only from the African legumes Acacia sieberiana var. woodii and Acacia hebeclada, has been isolated from an American species of the genus, Acacia constricta.     

Flavonol glycoside gallates from Tellima grandiflora

Quercetin 3-O-(6″-O-galloyl)-β-d-glucoside has been identified as a constituent of Tellima grandiflora (Saxifragaceae). In all, twelve gallates were encountered: two isomeric gallates of quercetin 3-O-glucoside and two of quercetin 3-O-galactoside, a similar set involving kaempferol, and a similar set involving myricetin.     

A glycosidic germacradienolide from Eupatorium altissimum

The isolation and structure determination of a glycosidic germacradienolide from Eupatorium altissimum are reported. Eupatorin and 5-hydroxy-3′,4′,6,7-tetramethoxyflavone were also found.     

Shapes and functions of species–area curves (II): a review of new models and parameterizations

This paper has extended and updated my earlier list and analysis of candidate models used in theoretical modelling and empirical examination of species–area relationships (SARs). I have also reviewed trivariate models that can be applied to include a second independent variable (in addition to area) and discussed extensively the justifications for fitting curves to SARs and the choice of model. There is also a summary of the characteristics of several new candidate models, especially extended power models, logarithmic models and parameterizations of the negative-exponential family and the logistic family. I have, moreover, examined the characteristics and shapes of trivariate linear, logarithmic and power models, including combination variables and interaction terms. The choice of models according to best fit may conflict with problems of non-normality or heteroscedasticity. The need to compare parameter estimates between data sets should also affect model choice. With few data points and large scatter, models with few parameters are often preferable. With narrow-scale windows, even inflexible models such as the power model and the logarithmic model may produce good fits, whereas with wider-scale windows where inflexible models do not fit well, more flexible models such as the second persistence (P2) model and the cumulative Weibull distribution may be preferable. When extrapolations and expected shapes are important, one should consider models with expected shapes, e.g. the power model for sample area curves and the P2 model for isolate curves. The choice of trivariate models poses special challenges, which one can more effectively evaluate by inspecting graphical plots.