Circadian rhythms are autonomous oscillators developed by the molecular circadian clock, essential for coordinating internal time with the external environment in a 24-h daily cycle. In mammals, this circadian clock system plays a major role in all physiological processes and severely affects human health. The regulation of the circadian clock extends beyond the clock genes to involve several clock-controlled genes. Hence, the aberrant expression of these clock genes leads to the downregulation of important targets that control the cell cycle and the ability to undergo apoptosis. This may lead to genomic instability and promotes carcinogenesis. Alteration in the clock genes and their modulation is recognized as a new approach for the development of effective treatment against several diseases, including cancer. Until now, there has been a lack of understanding of circadian rhythms and cancer disease. For that, this chapter aims to represent the core components of circadian rhythms and their function in cancer pathogenesis and progression. In addition, the clinical impacts, current clock drugs, and potential therapeutic targets have been discussed.
Currently, consumers' demand for sunscreens derived from natural sources that provide photoprotection from ultraviolet (UV) radiation is pushing the cosmetic industry to develop breakthrough formulations of sun protection products by incorporating plant antioxidants as their active ingredients. In this context, the present study was initiated to evaluate the antioxidant and photoprotective properties of the underutilized Hylocereus polyrhizus peel extract (HPPE) using in vitro spectrophotometric techniques. The phytochemical screenings of HPPE conducted via high-performance liquid chromatography (HPLC) and ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) revealed the presence of phenolic acids and flavonoids as the major secondary metabolites in HPPE. The antioxidant potentials evaluated based on 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical and total antioxidant capacity assays were in the range of 22.16 ± 0.24%-84.67 ± 0.03% with 50% inhibitory concentration (IC50) of 36.39 ± 0.04 μg/mL and 23.76 ± 0.14%-31.87 ± 0.26% (IC50 = 21.93 ± 0.07 μg/mL), respectively. For the photoprotective evaluation, the results showed that HPPE had significantly high absorbance values (3.1-3.6) at 290-320 nm with an exceptional sun protection factor (SPF) value of 35.02 ± 0.39 at 1.00 mg/mL. HPPE also possessed a broad-spectrum shielding power against both UVA and UVB radiations. Hence, in terms of practical implications, our findings would offer an exciting avenue to develop a photoprotective formulation incorporating the ethanolic extract of Hylocereus polyrhizus peels as a synergistic active ingredient for its excellent UV absorption properties and the strong antioxidant activities.