Abstract.We report extensive photometry of the dwarf nova QW Ser throughout its February 2003 superoutburst untill quiescence. During the superoutburst the star displayed clear superhumps with a mean period of P sh = 0.07703(4) days. In the quiescence we observed a double humped wave characterized by a period of P = 0.07457(2) days. As both periods obey the Stolz-Schoembs relation with a period excess equal to 3.30 ± 0.06%, the latter period is interpreted as the orbital period of the binary system

Silymarin, a mixture of flavonolignans exhibiting many pharmacological activities, is obtained from the fruits of milk thistle (Silybum marianum L. Gaertner). Due to the high lipid content in thistle fruits, the European Pharmacopoeia recommends a two-step process of its extraction. First, the fruits are defatted for 6 h, using n-hexane; second, silymarin is extracted with methanol for 5 more hours. The presented data show that this extremely long traditional Soxhlet extraction process can be shortened to a few minutes using pressurized liquid extraction (PLE). PLE also allows to eliminate the defatting stage required in the traditional procedure, thus simplifying the silymarin extraction procedure and preventing silymarin loss caused by defatting. The PLE recoveries obtained under the optimized extraction conditions are clearly better than the ones obtained by the Pharmacopoeia-recommended Soxhlet extraction procedure. The PLE yields of silychristin, silydianin, silybin A, silybin B, isosilybin A and isosilybin B in acetone are 3.3, 6.9, 3.3, 5.1, 2.6 and 1.5 mg/g of the non-defatted fruits, respectively. The 5-h Soxhlet extraction with methanol on defatted fruits gives only ∼72% of the silymarin amount obtained in 10 min PLE at 125°C.

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Context.We report an analysis of photometric behaviour of DI UMa, an extremely active dwarf nova. The observational campaign (completed in 2007) covers five superoutbursts and four normal outbursts. Aims. We examined principal parameters of the system to understand peculiarities of DI UMa, and other active cataclysmic variables. Methods. Based on precise photometric measurements, temporal light curve behaviour, O−C analysis, and power spectrum analysis, we investigated physical parameters of the system. Results. We found that the period of the supercycle now equals 31.45 ± 0.3 days. Observations during superoutbursts infer that the period of superhumps equals P sh = 0.055318(11) days (79.66 ± 0.02 min). During quiescence, the light curve reveals a modulation of period P orb = 0.054579(6) days (78.59 ± 0.01 min), which we interpret as the orbital period of the binary system. The values obtained allowed us to determine a fractional period excess of 1.35% ± 0.02%, which is surprisingly small compared to the usual value for dwarf novae (2%-5%). A detailed O−C analysis was performed for two superoutbursts with the most comprehensive coverage. In both cases, we detected an increase in the superhump period with a mean rate ofṖ/P sh = 4.4(1.0) × 10 −5 . Conclusions. Based on these measurements, we confirm that DI UMa is probably a period bouncer, an old system that reached its period minimum a long time ago, has a secondary that became a degenerate brown dwarf, the entire system evolving now toward longer periods. DI UMa is an extremely interesting object because we know only one more active ER UMa star with similar characteristics (IX Dra).