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Various environmental, physical and chemical stresses on cells may induce either an overproduction of ROS (Reactive Oxygen Species) or a deficiency of antioxidant enzymes. ROS are responsible for various cellular anomalies like protein damage, deactivation of enzymes, alteration of DNA and lipid peroxidation which in turn leads to pathological conditions like carcinogenesis, reperfusion injury, rheumatoid arthritis, diabetes etc. The regular intake of antioxidants seems to limit or prevent the dangerous effects caused by ROS. Thus, to maintain cellular health, it is important to have a specific and effective antioxidant that scavenges multiple types of free radicals so that it can be used in multiple diseases. Different in vitro and in vivo test systems are available in the literature to assess the free radical scavenging activity of various compounds. Based on the efficiency of free radical scavenging, the compounds are classified into strong, moderate and weak antioxidants. The following review explains the brief procedure and the principle behind various methods available in the literature, which can be used to determine the scavenging of different types of free radicals.

Sesamol has been studied extensively in the past two decades for its curative role in various diseases owing to its antioxidant potential. In vitro and in vivo pre-clinical studies indicate diverse role of sesamol in ailments connected by a common denominator of oxidative stress. These include antioxidant, anti-mutagenic, neuroprotective, hepatoprotective, cardioprotective, chemopreventive and anti-ageing properties. However, in depth investigation of its important characteristics including its oral pharmacokinetics is warranted, before evaluating this molecule for clinical application. The present study was undertaken to determine the physicochemical properties viz. solubility, log P, pK a and distribution coefficient of sesamol, coupled with its regional permeability through rat GIT. Single dose oral pharmacokinetic and tissue distribution studies of sesamol were also conducted in rats. The results indicate sesamol to be a molecule with appropriate aqueous solubility ($38.8 mg mL À1 ) and log P (1.29); the pK a of sesamol was found to be 9.79 and it exhibited a distribution coefficient of >1. Sesamol was well absorbed throughout the GIT and showed an oral bioavailability of 95.61%. Sesamol is widely distributed in rat tissue with the highest concentration in the kidneys followed by lungs, brain, and liver. In spite of a favorable bioprofile, the wide distribution, small t 1/2 and fast clearance of sesamol indicate a need for packaging it into a suitable delivery system.

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Role of reactive oxygen species (ROS) in skin carcinogenesis is well documented. Natural molecules, like sesamol, with marked antioxidant potential can be useful in combating skin cancers. In vitro antiproliferative (using MTT assay) and DNA fragmentation studies in HL 60 cell lines, confirmed the apoptotic nature of sesamol. However, it showed a significant flux across the mice skin upon topical application, such that its local availability in skin is limited. Former is attributed mainly to its properties like small size, low molecular weight (138.28), and a sufficient lipid and water solubility (log P 1.29; solubility 38.8 mg/ml). To achieve its maximum epicutaneous delivery, packaging it into a suitable carrier system is thus indicated. Sesamol-loaded solid lipid nanoparticles (S-SLN) were thus prepared with particle size of 127.9 nm (PI: 0.256) and entrapment efficiency of 88.21%. Topical application of S-SLN in a cream base indicated significant retention in the skin with minimal flux across skin as confirmed by the in-vivo skin retention and ex-vivo skin permeation studies. In vivo anticancer studies performed on TPA-induced and benzo(a)pyrene initiated tumour production (ROS mediated) in mouse epidermis showed the normalization (in histology studies) of skin cancers post their induction, upon treatment with S-SLN.

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