Besides the unquestionable positive effects of solar exposure for human health, UV rays have been widely investigated for toxicology aspects related to excessive UVB and UVA doses, which involve sunburns, skin aging, DNA skin damage and tumorigenesis. At present, synthetic and mineral sunscreens are used to protect against these damages but several natural molecules can provide UV protection, including also synergic effect or enhanced photo stability. Although a large number of herbal extracts and plant origin molecules can deserve potential applications, most of the study reported utilizes different method and different strategies of investigation, making thus difficult to understand the real versus claimed potential. This is possibly one of the reasons why, beside the large body of literature there are no officially approved natural commercial sun-filter but a consistent number of commercially available solar products (sunscreen) on the market that contain herbal derivatives. In this review we have evaluated the papers appeared in the last 15 years and we have critically collected the most significant data. Several databases, namely Scifinder, Pubmed, Google Scholar, ISI-Web of Science and Scopus, were used as literature sources; excluding patents and symposium or congress papers. Only articles in the English language have been selected. New formulation, new skin delivery systems, skin penetration enhancers and boosters are most likely the next frontier of investigation in order to better understand the role of whole herbal extracts in exerting their photo protective activity.
Growth of the chalcone isomerase defective tt-5 mutant of Arabidopsis thaliana and its Landsberg erecta progenitor were compared under a variety of full spectrum solar radiation conditions to determine if the tt-5 mutant could serve as an adequate subject for studies of the mechanisms of damage by UV-B radiation. An experiment was conducted in the fall of 1995 under open field filter frames using cellulose diacetate and Mylar filters to transmit and exclude natural UV-B irradiation, respectively. Even though growth under these conditions was slow and erratic owing to lack of temperature control, growth suppression as indicated by rosette diameter and harvest fresh weights provided a sensitive indicator of UV-B stress. This experience led to development of temperature-controlled Teflon-covered field chambers that admit up to 88% of the total daily PAR and about 85% of ambient UV-B, omit predators, and provide a generally stable environment for quantitative plant growth studies. The chambers were designed' to facilitate the addition of optical filters and/or shade cloth and to accommodate control of the gaseous environment for pollutant and climate change studies and to provide clean air for other experiments. Three additional experiments were conducted in these chambers. Measurements of rosette diameter, weights of various aboveground plant parts, and plant height were evaluated as potential methods of comparing growth sensitivities of the tt-5 mutant to UV-B radiation. The weight of the reproductive parts (flowers and siliques) as a fraction of the total (e.g. harvest index) was consistently and negatively affected by solar UV-B, as was simple plant height. However, in no case, even in the virtual absence of UV-B, was growth of tt-5 comparable to that of Ler. We conclude that the disruption of secondary metabolism in tt-5 has growth implications far beyond the lack of UV-B protection, making it unsuitable as a surrogate for high UV-B experimentation.
The growing concern over appearance, health and aging has driven the exploration for cosmetics based on natural sources. Alongside with plants, algae and eukaryotic microalgae, cyanobacteria have been explored for the isolation of compounds with potential application in the cosmetic and cosmeceutical field. The long evolutionary history of cyanobacteria and exposure to environmental stress conditions seems to be the basis for the production of compounds with protective roles against external factors, such as desiccation, UV radiation and salinity. The production of exopolysaccharides, UV-protectors such as mycrosporine like amino acids and scytonemin, and antioxidant and anti-inflammatory compounds, by a wide range of cyanobacteria genera, coupled with a growing demand for natural origin products, places these organisms in the investigation line linked to cosmetics. The low nutritional requirements for large scale culture and the possibility to increase compounds production by manipulating culture conditions, also highlights the importance of these organisms as an alternative and a promising source for cosmetics based on nature. In this review, a general overview of the state of the art regarding the potential of cyanobacteria for the cosmetic and cosmeceutical industry is provided, emphasizing the main properties required in skin care formulations.
Patches of vegetation of six common species growing on Léonie Island (67°35′ S, 68°20′ W), Antarctic Peninsula region were covered with either UV-B transparent perspex screens or UV-B absorbing screens. Uncovered plots served as a control. Temperature and relative humidity were monitored during the austral summer under and outside the screens. The mean effective PSII quantum efficiency showed significant differences among the species, but not between the UV-B treatments. It was concluded that the temperature and the moisture status of the vegetation obscured any possible influence of UV-B treatment on the tteffective PSII quantum efficiency. he usefulness of various UV-B exclusion and supplementation methods used to study the influence of UV-B in the field is discussed.
The physiological effects unique to solar ultraviolet (UV)‐B exposure (280–315 nm) are difficult to accurately replicate in the laboratory. This study evaluates the effectiveness of the sodium urate anion in a liquid filter that yields a spectrum nearly indistinguishable from the solar UV‐B spectrum while filtering the emissions of widely used UV‐B lamps. The photochemical properties and stability of this filter are examined and weighed against a typical spectrum of ground‐level solar UV‐B radiation. To test the effectiveness of this filter, light‐saturated photosynthetic oxygen evolution rates were measured following exposure to UV‐B filtered either by this urate filter or the widely used cellulose acetate (CA) filter. The ubiquitous marine Chlorophyte alga Dunaliella tertiolecta was tested under identical UV‐B flux densities coupled with ecologically realistic fluxes of UV‐A and visible radiation for 6 and 12 h exposures. These results indicate that the urate‐filtered UV‐B radiation yields minor photosynthetic inhibition when compared with exposures lacking in UV‐B. This is in agreement with published experiments using solar radiation. In sharp contrast, radiation filtered by CA filters produced large inhibition of photosynthesis.
▶ Ultraviolet radiation enhancs the morphogenetic effect of light. ▶ The epidermal content of phenols increases with light intensity, in parallel to the increase of leaf mass per area. ▶ High light increases the activity of end receptors in the electron transport chain, indicating a photochemical pathway for energy de-excitation connected. ▶ Plants grown in absence of UV radiation display a more effective response to light intensity variations. ▶ The absence of UV radiation in the Mediterranean environment reduce the level of acclimation to high light conditions. The aim of this study was to evaluate how different regimes of photosynthetic active radiation (PAR) impact leaves in UV filtered (−UV) and non-filtered (ambient light, AL) conditions. Two-year-old potted plants of (grapevine) were grown, during the 2007 season, at three different radiation regimes: 100% (full light, L), 50% (L1) and 20% (L2) of sunlight. L1 and L2 plants were shaded with black shading nets. For each light condition, a sample of plants were subjected to UV rays exclusion using filtering plastic films. The experimental set-up was located in the Chianti area (Tuscany, central Italy). Microclimatic parameters were constantly monitored in all experimental conditions, and solar radiations were characterized through spectroradiometric and radiometric measurements. Non-destructive measurements were performed during the experimental period (leaf epidermal flavonoid accumulation with Dualex; stomatal conductance with dynamic porometer) and, once, at the end of the experiment itself (fast kinetics of chlorophyll fluorescence with direct fluorimeter; chlorophyll content with chlorophyll-meter). Morphometric parameters (leaf mass per area, leaf density and thickness) were detected by destructive analysis at the end of the growing season. Full sunlight conditions induced the formation of thicker leaves, with higher leaf mass per area, as well as the accumulation of polyphenols (the latter were present in smaller amounts in plants exposed to UV filtration, −UV). Physiologically, plants exposed to full sunlight (L) showed lower quantum yield of primary photochemistry (F /F ), higher controlled dissipation from antenna complex of PSII and faster reduction of electron final acceptors side of PSI. These responses were more pronounced in the UV filtered plants. Ambient levels of UV, in this Mediterranean culture, induced morphological responses useful for acclimation in stressful conditions.