Journal of Chromatography A, 1054 (2004) 235–239 Evaluation of a methylation procedure to determine cyclopropenoids fatty acids from Sterculia striata St. Hil. Et Nauds seed oil Sabria Aued-Pimentel a,∗ , Jo˜ ao Henrique Ghilardi Lago b , Mariana Helena Chaves c , Edna Emy Kumagai a a Instituto Adolfo Lutz, Divis ˜ ao de Bromatologia e Qu´ ımica, C.P. 1783, 01059-970 S˜ ao Paulo, SP, Brazil b Instituto de Qu´ ımica, Universidade de S˜ ao Paulo, C.P. 26077, 05599-970 S˜ ao Paulo, SP, Brazil c Departamento de Qu´ ımica, Universidade Federal do Piau´ ı, Campus Ministro Petrˆ onio Portela, 64049-550 Teresina PI, Brazil Available online 11 September 2004 Abstract Cyclopropenoids fatty acids (CPFA) from Sterculia striata seed oil were characterized by gas chromatography/mass spectrometry (GC/MS) and quantified by gas chromatography–flame ionization detector (GC–FID) after derivation to fatty acid methyl esters using a cold base- catalyzed procedure. 1 H nuclear magnetic resonance (NMR) analysis were done in oil and fatty acid methyl esters derivatives to quantify CPFA and verify artifacts formation during the base-catalyzed reaction. Similar quantities of CPFA were found in S. striata and Sterculia foetida seed oils before and after a base-catalyzed methylation by NMR analysis, with no artifact formation. These results were compatible with those obtained by GC–FID analysis. Transmethylation with KOH in methanol was an appropriated method to prepare cyclopropenoids fatty acids methyl esters and quantify them by GC and NMR analysis. © 2004 Elsevier B.V. All rights reserved. Keywords: Cyclopropenoids fatty acids (CPFA); Sterculia striata; Methylation 1. Introduction Several studies on seeds of Sterculaceae, Malvaceae, Fil- iceae and Bombacaceae family describe the occurrence of cyclopropenoid fatty acid derivatives. The most commonly ones found are sterculic (9,10-methylene-9-octadecenoic) and malvalic (8,9-methylene-8-heptadecenoic) acids [1,2]. Studies with the oil from seeds of S. foetida, S. tomentosa and S. tragacanta (Sterculaceae) have reported high content of cyclopropenoids fatty acids (CPFA) [3,4]. Compounds containing cyclopropenoid ring are associated with several biological properties, such as: insecticide, antifungal, antibiotic, antiviral, hormonal, carcinogenic or antitumoral activities and enzyme inhibitor [5,6]. The effects of CPFA in animals have been the subject of several investigations, including co-carcinogenic and carcinogenic activities [7–9]. Sterculic acid is an inhibitor of  9 -desaturase which converts ∗ Corresponding author. Tel.: +55 11 3814 7977; fax: +55 11 3085 3505. E-mail addresses: spmente@ial.sp.gov.br, sabria aued@yahoo.com (S. Aued-Pimentel). stearic acid into oleic acid and is potentially noxious to man, since it can alter the cellular membranes permeability and inhibit the cellular reproduction [10]. The “chich´ a” nut, or Sterculia striata seed, also known in Brazil as “amendoim-da-mata” and “castanha de macaco” [11], is consumed raw by the fauna and cooked or toasted by man [12]. Some nutritional features of “chich´ a” nuts were evaluated by Oliveira et al. [13], in which several macronu- trients such as lipids (28.6%), protein (22.5%) and carbohy- drates (45.8%), were quantified. We have reported previously some physical and chemical characteristics of S. striata seed oil and verified the occurrence of CPFA [14]. CPFA are labile compounds and there are several ana- lytical problems to determine these compounds using gas chromatography. The cyclopropenoid groups are destroyed by heating and acid media during extraction and esterifica- tion process [9]. CPFA can also be decomposed thermally in the injector or in polar columns during the GC analysis. The main methods used for the analysis of CPFA are hydro- gen bromide titration, nuclear magnetic resonance (NMR), selective derivations followed by gas chromatographic 0021-9673/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2004.07.090