Variabilidad en compuestos fenólicos del residuo hidrodestilado de "Thymus mastichina"

Résumé

Most of antioxidants used by industry are synthetic and their use is controversial, so it might be highly desirable to find out natural compounds with antioxidant activity. Owing to this, the antioxidant activity of extracts from several Lamiaceae species have been evaluated, including Thymus mastichina, but less information is available about the phenolic composition of extracts from this species. As essential oil of T. mastichina is used by perfume and cosmetic industry, the hydrodistilled residue could be revalued as source of antioxidant compounds. In 2008, samples of plant material from 46 wild populations of Spanish marjoram have been collected around the nine provinces of Castilla y León. After extracted the essential oil by hydrodistillation in Clevenger, the waste was dried and ground. Phenol compounds were extracted with methanol in a Soxlet apparatus and a rotary evaporator. The contents of dry extracts in flavonoids and organic acids were determined by a High Performance Liquid Chromatograph (HPLC) with a Diode Array Detector (DAD). Compounds identification was done by comparing with pure standards. To study the variability among the samples analyzed and the compounds that influence in that variability, a cluster and principal component analysis have been calculated. The total content of evaluated phenol compounds ranged from 272 (TM-10, Villamayor, Salamanca) to 1298 (TM-45, Salinas de Pisuerga, Palencia) mg/g of dry extract. Of the 18 evaluated compounds, 14 were detected, 5 in significant amounts: apigenin, kampherol, luteolin, and 3-metixisalicilic and rosmarinic acids. The main phenol component detected was rosmarinic acid (ranging between 89 and 985 mg/g of dry extract), followed by 3-metoxisalicilic acid (49-214 mg/g of dry extract). The principal component analysis reported that kampherol, apigenin and luteolin provide more variability to the set of samples evaluated, than the most abundant compounds, 3-metoxisalicilic and rosmarinic acids. The cluster analysis showed that samples could be distributed in three groups. Group 1 was characterized by a low content of total phenols and grouped 16 populations. Group 2, the largest one formed by 23 populations, was highlighted by the large amount of 3- metoxisalicilic and rosmarinic acids. Finally, the 7 populations grouped in group 3 showed high content in apigenin, kampherol and luteolin.