In the last 10 years there has been an increased interest in using techniques involving microwave-assisted extraction and pressurised solvent extraction in analytical laboratories. This review gives a brief overview of both methods, and reports on their application to the extraction of natural products. The influence of parameters such as the nature of the solvent and volume, temperature, time and particle size of the matrix is discussed. Through numerous examples, it is demonstrated that both techniques allow reduced solvent consumption and shorter extraction times, while the extraction yields of the analytes are equivalent to or even higher than those obtained with conventional methods.

Focused microwave-assisted extraction was applied to the extraction of three main withanolides from airdried leaves of Iochroma gesnerioides, namely, withaferin A, iochromolide and withacnistin. Six extraction variables, i.e. nature and volume of extracting solvent, sample moisture, extraction time, power of irradiation and particle size, were investigated with respect to the recovery of withanolides. The most favourable conditions were obtained by using powdered plant material (< 220 microns), previously impregnated with water for 15 min, and extracted with methanol for 40 s at 25 W. The results obtained using the optimised method were compared to those achievable with Soxhlet extraction.

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Mineralocorticoid receptor (MR) contributes to retinal/choroidal homeostasis. Excess MR activation has been shown to be involved in pathogenesis of central serous chorioretinopathy (CSCR). Systemic administration of MR antagonist (MRA) reduces subretinal fluid and choroidal vasodilation, and improves the visual acuity in CSCR patients. To achieve long term beneficial effects in the eye while avoiding systemic side-effects, we propose the use of biodegradable spironolactone-loaded poly-lactic-co-glycolic acid (PLGA) microspheres (MSs). In this work we have evaluated the ocular tolerance of MSs containing spironolactone in rat' eyes. As previous step, we have also studied the tolerance of the commercial solution of canrenoate salt, active metabolite of spironolactone. PLGA MSs allowed in vitro sustained release of spironolactone for 30days. Rat eyes injected with high intravitreous concentration of PLGA MSs (10mg/mL) unloaded and loaded with spironolactone maintained intact retinal lamination at 1month. However enhanced glial fibrillary acidic protein immunostaining and activated microglia/macrophages witness retinal stress were observed. ERG also showed impaired photoreceptor function. Intravitreous PLGA MSs concentration of 2mg/mL unloaded and loaded with spironolactone resulted well tolerated. We observed reduced microglial/macrophage activation in rat retina compared to high concentration of MSs with normal retinal function according to ERG. Spironolactone released from low concentration of MSs was active in the rat retina. Low concentration of spironolactone-loaded PLGA MSs could be a safe therapeutic choice for chorioretinal disorders in which illicit MR activation could be pathogenic.