Photoprotective Activity of Plectranthus amboinicus Extracts and HPLC Quantification of Rosmarinic Acid

Abstract

Overexposure to sunlight has harmful effects on the skin and can cause erythema and skin cancer. Photoprotective agents are important for preventing exposure to sunlight and are present in the composition of sunscreens. Globally, the use of filters based on natural products has gained interest in scientific studies; in addition to their sunscreen properties, these products demonstrate antioxidant, healing, and moisturizing activity. These favor adequate sun protection due to the wide spectrum of activities and are environmentally friendly. Plectranthus amboinicus (Lour.) Spreng., Lamiaceae, is used in traditional medicine to treat several conditions and is commonly known as "hortelã-da-folha-grossa" in Brazil. This species presents phenolic compounds, including rosmarinic acid, and has been studied for photoprotection and antioxidant activity. The aim of this study was to evaluate the photoprotection potential and antioxidant activity, and to develop analytic methodology for extract standardization and validation. Thus, maximum absorbance, sun protection factor, DPPH radical scavenging activity, and total phenolic contents of P. amboinicus crude ethanolic extract were determined, and an HPLC analytical methodology was developed and validated to quantify rosmarinic acid. Analyses revealed that the extract presented good photoprotection (SPF = 12.63), promising antioxidant activity (EC 50 = 112.39 μg/ml), total phenolic content (142.39 ± 1.12 mg GAE/g), and rosmarinic acid concentrations (22.5 μg/ml). In addition, an HPLC analytical method was validated for marker quantification. These results show that the extract has potential photoprotective and antioxidant activity, and this favors the isolation of a final product with protective characteristics that encompass broad spectrum action and biological protection.

Seasonal Variations of Polyphenols Content, Sun Protection Factor and Antioxidant Activity of Two Lamiaceae Species

“…According to a previous study by Terto et al [ 40 ] and unpublished data [ 41 ], it was seen that RA was the most produced compound in CEE of aerial parts of M. villosa and P. amboinicus , and so because of this, its variation was also evaluated. Thus, it was observed that P. amboinicus had the highest concentrations of this metabolite in a good part of the year and the only month that there was no statistical difference in RA content between the two species was August, when they showed statistically equal production, as shown in Figure 3 .…”

“…For extract samples of P. amboinicus , a diluent solution used was MeOH:acidified water (0.1% of formic acid) 1:1, the run starts at 50% of solvent B and reaches 60% in 20 min, returning to 50% in 21 min and remaining at this concentration until the end, at 26 min. In this case, the flow rate used was 0.6 mL/min [ 40 ].…”

“…As observed for total polyphenols content, when the two species are evaluated individually, it was seen that there was no statistical difference of flavonoids concentration in several months of different seasons in M. villosa and P. amboinicus, indicating that their production also did not obey a specific trend to each season, which shows that seasons seem to have less influence in variation of flavonoids quantitatively production. According to a previous study by Terto et al [40] and unpublished data [41], it was seen that RA was the most produced compound in CEE of aerial parts of M. villosa and P. As observed for total polyphenols content, when the two species are evaluated individually, it was seen that there was no statistical difference of flavonoids concentration in several months of different seasons in M. villosa and P. amboinicus, indicating that their production also did not obey a specific trend to each season, which shows that seasons seem to have less influence in variation of flavonoids quantitatively production.…”

“…Therefore, understanding the annual variations of secondary metabolites of these two species can help us to better use them in terms of pharmaceutical product development. A previous study by Terto et al [ 40 ], as well as unpublished data [ 41 ], showed that these two species have promising photoprotective activity in vitro since they presented a sun protection factor (SPF) of around 13. Thus, we evaluated the seasonal variations that occurred in M. x villosa and P. amboinicus , by monitoring the quantitative production of polyphenols, flavonoids, and rosmarinic acid month by month, the role of solar radiation, and precipitation in the production of these metabolites and their implications for the SPF and antioxidant activity of these extracts.…”

Antibacterial, antioxidant, and sun protection potential of selected ethno medicinal plants used for skin infections in Uganda

“…The antioxidant activity of the selected plants was comparable to plants from the same genus. For example, S. articular and S. exilis have inhibited nitric oxide accumulation in cell cultures at 125 μg/ml [ 33 ], methanolic extracts of P. febrifugum exhibited antioxidant activity at 0.02 mg/ml [ 14 ] whereas P. amboinicus has shown promising antioxidant activity at 112.39 μg/ml [ 39 ].…”