Phyllanthus orbicularis (Phyllanthaceae) is an endemic evergreen tropical plant of Cuba that grows in the western part of the island and is used in traditional medicine as an infusion. The aqueous extract of this plant presents a wide range of pharmacological activitiessuch as antimutagenic, antioxidant and antiviral effects. Given the many beneficial effects and the great interest in the development of new pharmacological products from natural sources, the aim of this work was to investigate the phytochemistry of this species and to elucidate the structure of the main bioactive principles. Besides the presence of several known polyphenols, the major constituent was hitherto not described. The chemical structure of this compound, here named Fideloside, was elucidated by means of HR-ESIMS/MSⁿ, 1D/2D NMR, FT-IR, and ECD as (2R,3R)-(−)-3’,4′,5,7-tetrahydroxydihydroflavonol-8-C-β-D-glucopyranoside. The compound, as well as the plant aqueous preparations, showed promising bioactive properties, i.e., anti-inflammatory capacity in human explanted monocytes, corroborating future pharmacological use for this new natural C-glycosyl flavanonol.

Context: One approach to protect human skin against the dangerous effects of solar ultraviolet (UV) irradiation is the use of natural products, such as photoprotectors. Phyllanthus orbicularis Kunth (Euphorbiaceae) is a Cuban endemic plant used in popular medicine. Its antigenotoxicity effect against some harmful agents has been investigated. However, the effect in ultraviolet B (UVB)-irradiated human cells has not been previously assessed. Objective: The protective effect of a P. orbicularis extract against UVB light-induced damage in human cells was evaluated. Materials and methods: DNA repair proficient (MRC5-SV) and deficient (XP4PA, complementation group XPC) cell-lines were used. Damaging effects of UVB light were evaluated by clonogenic assay and apoptosis induction by flow cytometry techniques. The extent of DNA repair itself was determined by the removal of cyclobutane pyrimidine dimers (CPDs). The CPDs were detected and quantified by slot-blot assay. Results: Treatment of UVB-irradiated MRC5-SV cells with P. orbicularis extract increased the percentage of colony-forming cells from 36.03 ± 3.59 and 4.42 ± 1.45 to 53.14 ± 8.8 and 14.52 ± 1.97, for 400 and 600 J/m², respectively. A decrease in apoptotic cell population was observed in cells maintained within the extract. The P. orbicularis extract enhanced the removal of CPD from genomic DNA. The CPDs remaining were found to be about 27.7 and 1.1%, while with plant extract, treatment these values decreased to 16.1 and 0.2%, for 3 and 24 h, respectively. Discussion and conclusion: P. orbicularis aqueous extract protects human cells against UVB damage. This protective effect is through the modulation of DNA repair effectiveness.