Aging of skin is an intricate biological process consisting of two types. While intrinsic or chronological aging is an inevitable process, photoaging involves the premature aging of skin occurring due to cumulative exposure to ultraviolet radiation. Chronological and photoaging both have clinically differentiable manifestations. Various natural and synthetic retinoids have been explored for the treatment of aging and many of them have shown histological and clinical improvement, but most of the studies have been carried out in patients presenting with photoaged skin. Amongst the retinoids, tretinoin possibly is the most potent and certainly the most widely investigated retinoid for photoaging therapy. Although retinoids show promise in the treatment of skin aging, irritant reactions such as burning, scaling or dermatitis associated with retinoid therapy limit their acceptance by patients. This problem is more prominent with tretinoin and tazarotene whereas other retinoids mainly represented by retinaldehyde and retinol are considerably less irritating. In order to minimize these side effects, various novel drug delivery systems have been developed. In particular, nanoparticles have shown a good potential in improving the stability, tolerability and efficacy of retinoids like tretinoin and retinol. However, more elaborate clinical studies are required to confirm their advantage in the delivery of topical retinoids.

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Epalrestat is a new drug for diabetic neuropathy. A new, simple, rapid very sensitive, and accurate high performance thin-layer chromatographic (HPTLC) method has been developed and validated for estimation of epalrestat in plasma. HPTLC was performed on silica gel 60F 254 plates with ethyl acetate-toluene-acetic acid, 60 + 40 + 2 (v/v), as mobile phase. Nitrofurantoin was used as internal standard. Densitometric scanning was performed in absorbance mode at λ λ = 390 nm. The R F values of the internal standard and drug were 0.4 and 0.6, respectively. The response was a linear function of concentration over the range 0.1-6.0 μg mL -1 (r 2 = 0.9974). Mean extraction recovery was >63%. Intra-day and inter-day precision (% CV) of the assay were in the range 1.62-4.68% and accuracy was >95%. This method can be applied to pharmacokinetic and bioequivalence studies. Preparation of Calibration Standard Solutions in PlasmaCalibration standards were prepared by spiking drug-free plasma with epalrestat working standard solution (100 μg mL -1 , 60 μL) to furnish a 6 μg mL -1 calibration standard. This solution was further diluted with drug-free plasma to furnish calibration

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