Comparisons between conventional, ultrasound-assisted and microwave-assisted methods for extraction of anthraquinones from Heterophyllaea pustulata Hook f. (Rubiaceae).

This work reports a comparative study about extraction methods used to obtain anthraquinones (AQs) from stems and leaves of Heterophyllae pustulata Hook (Rubiáceae). One of the conventional procedures used to extract these metabolites from a vegetable matrix is by successive Soxhlet extractions with solvents of increasing polarity: starting with hexane to eliminate chlorophylls and fatty components, following by benzene and finally ethyl acetate. However, this technique shows a low extraction yield of total AQs, and consumes large quantities of solvent and time. Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) have been investigated as alternative methods to extract these compounds, using the same sequence of solvents. It was found that UAE increases the extraction yield of total AQs and reduces the time and amount of solvent used. Nevertheless, the combination UAE with benzene, plus MAE with ethyl acetate at a constant power of 900 W showed the best results. A higher yield of total AQs was obtained in less time and using the same amount of solvent that UAE. The optimal conditions for this latter procedure were UAE with benzene at 50 °C during 60 min, followed by MAE at 900 W during 15 min using ethyl acetate as extraction solvent.

Quercetin 3,7,3',4'-tetrasulphated isolated from Flaveria bidentis inhibits tissue factor expression in human monocyte.

Sulphated esters of the flavonoids sulphated quercetin 3,7,3',4'-tetrasulphated (QTS) and quercetin 3-acetyl-7,3,4'-trisulphate (ATS), isolated from Flaveria bidentis, have demonstrated anticoagulant and antiplatelet properties. In this study, we examined if both compounds affected the expression of the procoagulant tissue factor (TF) induced by lipopolysaccharide (LPS) on human monocyte. Monocytes were pretreated with different concentrations of each flavonoid (0.1-500 µM), followed by a 4h incubation with LPS in order to induce TF expression. Results of the TF expression showed different behaviors for the two flavonoids studied. A slight inhibitory effect on the TF expression was detected at a QTS concentration of 0.1 µM, but from 1 µM onwards a significant inhibitory effect that remained up to 500 µM could be observed. In contrast, ATS induced a poor inhibitory effect on TF expression at all concentrations tested. These results suggest that QTS has another antithrombotic property, to be added to its already renowned ability as an anticoagulant and antiplatelet compound.

Photodynamic activity of anthraquinones isolated from Heterophyllaea pustulata Hook f. (Rubiaceae) on MCF-7c3 breast cancer cells.

Searching for agents that could be effective in the treatment of cancer, special highlight has focused on the study of numerous plant-derived compounds. We previously demonstrated that anthraquinones (AQs) isolated from a vegetal species: Heterophyllaea pustulata Hook f. (Rubiaceae), such as rubiadin, rubiadin-1-methyl ether, soranjidiol, soranjidiol-1-methyl ether exhibit photosensitizing properties without antecedents as photodynamic agents in malignant cells. In the present study, we investigated the potential role of these AQs as a phototoxic agent against human breast carcinoma using MCF-7c3 cells. All AQs exhibited significant photocytotoxicity on cancer cells at the concentration of 100 µM with 1 J/cm(2) light dose, resulting soranjidiol-1-methyl ether in complete cell destruction. The observed cellular killing by photoactivated AQs exhibited close relation with singlet oxygen production, except for soranjidiol-1-methyl ether, where cell viability decrease is in relation to uptake by tumor cells.

Pharmacological and toxicological activity of Heterophyllaea pustulata anthraquinone extracts.

Benzenic extracts from both stems and leaves of Heterophyllaea pustulata showed the most significant activity in vivo in the Brine Shrimp Lethally Test (BST), relative to others of different polarity. They were therefore selected for in vitro antimicrobial activity studies. Bacteriostatic activity against Micrococcus luteus ATCC 9341 was detected, selectively inhibiting both oxacillin-sensitive and -resistant Staphylococcus aureus, among several gram-positive and gram-negative bacterial species tested. Antifungal activity against important opportunist microorganisms and against those involved in superficial mycosis, all from nosocomial origin was also detected. A chemical screening revealed the presence of anthraquinones as major compounds. Among them, we identified damnacanthal, rubiadin, 2-hydroxy-3-methyl anthraquinone, soranjidiol, rubiadin-1-methyl ether, and damnacanthol in the benzenic stem extract. The benzenic leaf extract shows a similar chemical composition, except for damnacanthal, damnacanthol, soranjidiol-1-methyl ether, and 3 anthraquinones whose structures have not yet been elucidated. Acute toxicity studies revealed a low toxicity in mice for the anthraquinonic extracts, as measured in the LD50 value (123 mg/kg body wt. i.v.), and death was not observed at doses of up to 4000 mg/kg body wt. s.c.