International Journal of Pharmaceutics 303 (2005) 125–131 Chemical stability and SPF determination of Pothomorphe umbellata extract gel and photostability of 4-nerolidylcathecol Vanessa V. da Silva ∗ , Cristina D. Ropke, Rebeca L. de Almeida, Denise V. Miranda, ClarissaZ. Kera, Diogo P. Rivelli, Tˆ ania C.H. Sawada, Silvia B.M. Barros Departamento de An´ alises Cl´ ınicas e Toxicol´ ogicas, School of Pharmaceutical Sciences, University of S˜ ao Paulo, Av. Prof. Lineu Prestes, 580, 05508-000 S˜ ao Paulo, SP, Brazil Received 13 June 2005; received in revised form 7 July 2005; accepted 11 July 2005 Available online 29 August 2005 Abstract Due to its antioxidant and photoprotective properties, Pothomorphe umbellata is a promising candidate for use in cosmetic and pharmaceutical formulations. These properties arise from the presence of 4-nerolidylcathecol (4-NC), a polyphenolic compound isolated from P. umbellata roots. This study investigates its photostability properties, as well as the chemical and the in vitro sun protection factor (SPF) of P. umbellata root extract in a gel formulation. A high performance liquid chromatography method was used to evaluate the chemical stability using 4-NC as marker at 5, 25 and 45 ◦ C for 103 days. The photostability and the sun protection factor were analyzed by ultraviolet (UV) spectophotometry using samples irradiated with UVB lamp. No significant difference of the 4-NC concentration was found in formulations stored at 5 and 25 ◦ C. All samples stored at 45 ◦ C, however, showed degradation of gel structure. After 2 h of UVB exposure, there was no change in the absorption profile of 4-NC. The sun protection factor of P. umbellata root extract gel to final concentration of 0.1% 4-NC was not expressive (SPF = 3.35 ± 0.02), suggesting the predominance of its antioxidant activity. © 2005 Elsevier B.V. All rights reserved. Keywords: Pothomorphe umbellata; 4-Nerolidylcathecol; Stability; Photostability; Sun protection factor 1. Introduction Chronic exposure of human skin to solar ultraviolet (UV) radiation may cause several skin damages. These ∗ Corresponding author. Tel.: +55 11 3091 3631; fax: +55 11 3813 2197. E-mail address: vavitoria@usp.br (V.V. da Silva). damages include sunburn, skin cancer, oxidative stress as well as photoaging depending on the amount and form of the UV radiation and on the type of the indi- vidual exposed (Ichihashi et al., 2003; Melnikova and Ananthaswamy, 2005). There has been an increasing interest in the use of antioxidants in sunscreens to provide supplemen- tal photoprotective action activity. Antioxidants from 0378-5173/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpharm.2005.07.006