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6α,7β-Dihydroxyvouacapan-17β-oic acid (1) was isolated from Pterodon polygalaeflorus Benth. Modification of 1 yielded 6α-hydroxyvouacapan-7β,17β-lactone (2) and then 6-oxovouacapan- 7β,17β-lactone (3). Photosynthesis inhibition by 3 was evaluated in spinach chloroplasts. The uncoupled non-cyclic electron transport rate and ATP synthesis were inhibited by 3, which behaved as a Hill reaction inhibitor. Furthermore, 3 acted as an uncoupler because it enhanced the basal and phosphorylating electron transport rate on thylakoids. This last property of 3 was corroborated when it was observed that it enhances the Mg2+-ATPase activity. In contrast, 3 did not affect photosystem I (PSI) activity. Analysis of the partial photosystem II (PSII) reactions from water to DCPIPox and water to silicomolybdate allowed to locate the inhibition sites at the redox components of PSII. The OJIP test of the chlorophyll a fluorescence transient confirmed that the inhibition sites were 1.) the oxygen-evolving complex (OEC) and 2.) by the formation of silent centers in the non-QA reducing centers.

ABSTRACT. Plants such as Annona nutans used in folk medicine have a large number of biologically active compounds with pharmacological and/or toxic potential. Moreover, pregnant women use these plants indiscriminately, mainly in the form of teas, without being aware of the harm that they could cause to the health of the embryo/fetus. Therefore, it is necessary to analyze the potential toxic effects of medicinal plants during gestation. The present study aimed to evaluate the effects of A. nutans hydromethanolic fraction leaves (ANHMF) on mutagenic and immunomodulatory activity, reproductive performance, and embryo-fetal development in pregnant female mice. The animals (N = 50 female and 25 male) were divided into 5 groups: Control, Pre-treatment, Organogenesis, Gestational, and Pre+Gestational. The results indicate that ANHMF mainly contains flavonoid and other phenolic derivatives. It was found that it does not exhibit any mutagenic or immunomodulatory activity, and it does not cause embryo-fetal toxicity. Based on the protocols used in the present studies, our analyses confirm that it is safe to use ANHMF during pregnancy.

This work describes the synthesis of new derivatives of 6a,7b-dihydroxyvouacapan-17b-oic acid (1) employing the Swern method for the oxidation of C-6 and C-7 of methyl 6a,7b-di-hydroxyvouacapan-17b-oate (2) and the formation of methyl 6,7-dioxovouacapan-17b-oate (3). NMR structural studies associated with theoretical calculations of reaction intermediates and products are also reported. The mixture of methyl 7b-hydroxy-6-oxovouacapan-17b-oate (4; 21%) and methyl 6a-hydroxy-7-oxovouacapan-17b-oate (5; 79%) was the product from the first step of the oxidation of 2. The lower energy of 5, calculated by HF/6-31G* and DFT/BLYP/6-31G* methods, reinforces the thermodynamic control proposed for the reaction. After further Swern oxidation of the mixture of 4 and 5, the isomeric form methyl 6-hydroxy-7-oxovouacap-5-en-17b-oate (6) was obtained. Theoretical calculations indicate a lower energy for the mono-enol 6 than the 1,2-diketo 3 and the other mono-enol methyl 7-hydroxy-6-oxovouacap-7-en-17b-oate (7).