Saponins, classification and occurrence in the plant kingdom

Haslam’s previous accounts of this area of flavonoid chemistry (Haslam, 1975, 1982a) eloquently summarized the historical developments in the chemistry and biochemistry of this important and complex group of plant phenolics. Also covered were their relationship with condensed tannins and aspects of their characteristic chemical and spectroscopic properties and metabolism.

Flavans and proanthocyanidins

Morin is a natural polyphenol, originally isolated from members of the Moraceae family that can be extracted from leaves, fruits, stems and branches of numerous plants. Several evidence have demonstrated that Morin could have a beneficial effect on several human diseases. In fact, Morin exerts antioxidant, antidiabetic, anti-inflammatory, antitumoral, antihypertensive, antibacterial, hypouricemic, and neuroprotective effects, by modulating the activity of many enzymes. In some cases, Morin shows a systemic protective action, reducing negative side effects of several drugs, without interfering with their functions. In addition, in vitro and in vivo studies demonstrated that Morin exhibits very low toxicity levels and its chronic administration is well tolerated. All these findings suggest that Morin could be used, either alone or in combination with other drugs, to prevent many human pathologies.

Morin: A Promising Natural Drug.

Summary 1. We tested a set of hypotheses to predict egg-laying behaviour in Aedes tr.isevintus in the field in Massachusetts. These hypotheses reflect three main themes: females avoid competitive or predatory threats to their larvae; feinales judge larvae or eggs as cues to future perinaileilce or productivity within a treehole; and females are either opportunistic ovipositors, or hedge their bets by scattering their eggs in multiple habitats. We predicted that ~nosquitoes might vary in their response depeilding on whether their offspring will hatch immediately or enter diapause and hatch the next year. 2. We stocked artificial treeholes with larvae at four densities ranging froin 0 to 90 larvae per habitat for four trials in 1992 and eight trials in 1994. In 1992, we added predatory Anopheles barbevi larvae to half the replicates of each density level. 111 1994, we tested for an interactio~l between egg and larval density by stocking additional traps with eggs in batches of 0, 20 and 200, and larvae in densities as in the previous trials. 3. The population revealed a significant interaction between time of year and larval density. More eggs accumulated in traps stocked with fewer larvae (0 or 15) early in the season, but fenlales showed a slight positive response to higher densities (45 or 90) later on, after their offspring were all likely to enter diapause. These results suggest that potential ambiguities of larval cues, with indications of habitat permanence as well as adversity of future competition, are resolved by females. Fenlales did not respoild differentially to the predatory Anopheles barberi larvae. 4. The estimated batch size obtained in oviposition traps did not differ from the fecundity of field-caught fe~nales allowed to oviposit under confinenlent in laboratory vials, suggesting that bet-hedging by scattering of eggs anlong multiple habitats did not occur. 5. An unexpected result, a positive response to higher egg densities, is discussed in light of studies on other insects. This result conflicts with our predictions based 011 fe~nales choosing less competitive environn~ents for their larvae and also co~lflicts with previously published accounts of avoidance of eggs in this species. Preference for habitats with conspecific eggs inight be explained if eggs reflect habitat stability or if larvae gain an advantage fro~n being in an aggregation. Neither hypothesis is resolved by the present study. Key-iuovds: Aedes, competitioi~, density-dependent, habitat selection, oviposition

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A seasonal shift in egg-laying behaviour in response to cues of future competition in a treehole mosquito

Ampelozizyphus amazonicus Ducke is a tree commonly found in the Amazon region and an extract of its stem bark is popularly used as an antimalarial and anti-inflammatory agent and as an antidote to snake venom. Ursolic acid; five lupane type triterpenes: betulin, betulinic acid, lupenone, 3beta-hydroxylup-20(29)-ene-27,28-dioic acid, and 2alpha,3beta-dihydroxylup-20(29)-ene-27,28-dioic acid, and three phytosteroids: stigmasterol, sitosterol and campesterol, have been isolated from stem extracts of A. amazonicus Ducke. Their structures were characterized by spectral data including COSY and HMQC. In an in vitro biological screening of the isolated compounds, 3beta-hydroxylup-20(29)-ene-27,28-dioic acid was cytotoxic against the SKBR-3 human adenocarcinoma cell line (1 to 10 mg/mL), while 2alpha,3beta-dihydroxylup-20(29)-ene-27,28-dioic acid exhibited cytotoxicity against both SKBR-3 human adenocarcinoma and C-8161 human melanoma tumor cell lines (>0.1 mg/mL). In the present study, different extracts and some fractions of this plant were also investigated for trypanocidal activity due to the presence of pentacyclic triterpenes. The triterpene classes are potent against Trypanosoma cruzi. The bioassays were carried out using blood collected from Swiss albino mice by cardiac puncture during the parasitemic peak (7th day) after infection with the Y strain of T. cruzi. The results obtained showed that A. amazonicus is a potential source of bioactive compounds since its extracts and fractions isolated from it exhibited in vitro parasite lysis against trypomastigote forms of T. cruzi at concentrations >100 microg/mL. Fractions containing mainly betulin, lupenone, 3beta-hydroxylup-20(29)-ene-27,28-dioic acid, and 2alpha,3beta-dihydroxylup-20(29)-ene-27,28-dioic acid showed more activity than crude extracts.

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In vitro evaluation of the cytotoxic and trypanocidal activities of Ampelozizyphus amazonicus (Rhamnaceae)

A dammarane-type saponin from the roots of Ampelozizyphus amazonicus

New peltogynoids from three Peltogyne species

The flavonoids kaempherol, genistein, naringenin, quercetin, morin, rutin and quercitrin isolated from UFV-5’soybean’s cultivars were tested as inhibitors of aldose reductase. The best results were obtained by using morin and quercitrin.

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Inhibitory action on aldose reductase by soybean flavonoids

Several larval and pupal products of Aedes fluviatilis (Lutz) were tested for their influence on the oviposition behaviour of females of the same species. Significant (alfa = 0,05) atractiveness was shown by: larval water, previously containing 5 to 15 larvae/1,5 ml; larval water, preserved up to 38 days; evaporate and reconstructed larval water extracts up to 2 years after production and water filtered through fresh or dried ground larvae. hexanic larval water extracts and water filtered through fresh or dired ground pupae did not influence oviposition.

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Influence of larval and pupal products on the oviposition behavior of Aedes Fluviatilis (Lutz) (Diptera: Culicidae)

O objetivo deste trabalho foi verificar o efeito antioxidante de derivados flavonoidicos da quercetina, naringenina, morina, e rutina, isolados da cultivar de soja UFV-5. Apos acetilacao com anidrido acetico e piridina, e metilacao com diazometano, esses compostos foram analisados para determinacao de acao antioxidante por meio dos indices de acidez, iodo e peroxido e pela reacao-de-Kreiss. Os melhores resultados foram obtidos com a naringenina metilada, naringenina acetilada, quercetina metilada e quercetina acetilada.

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Marco Antônio Teixeira

Papers

A dammarane-type saponin from the roots of Ampelozizyphus amazonicus

New peltogynoids from three Peltogyne species

Inhibitory action on aldose reductase by soybean flavonoids

Influence of larval and pupal products on the oviposition behavior of Aedes Fluviatilis (Lutz) (Diptera: Culicidae)

Ação antioxidante de flavonóides modificados