Antioxidant capacity variation in the oregano (Origanum vulgare L.) collection of the German National Genebank

Oregano (Origanum vulgare L.) is the most favorite spice plant for the production of natural antioxidants which may vary considerably among different varieties, landraces and accessions. Genetic variability in antioxidant capacity of oregano accessions from German National Genebank was studied by measuring oxygen radical absorbance capacity (ORAC), total phenolic content (TPC), rosmarinic acid content and essential oil content. In total, 42 accessions of Origanum vulgare from oregano collection of the genebank in Gatersleben (Germany) were evaluated. Of these 42 accessions, 19 accessions belonged to subspecies vulgare, 6 accessions to viride, 2 accessions to virens, 3 accessions to hirtum and 1 accession to gracile. The subspecies, to which the remaining 11 accessions belonged, were not known. The plants were cultivated in a pot experiment with 8–10 replications for each accession at the research station Rauischholzhausen from 2007 to 2008. The aerial parts of plants were harvested at the full flowering stage. The results demonstrated a broad variability among accessions and subspecies. The difference between the highest and lowest values was 2-fold for ORAC and TPC, while 6-fold differences were found for rosmarinic acid content. For essential oil content the differences between the lowest and highest values were almost 100-fold. The correlation between ORAC and TPC was moderately close (r=0.60, n=352). Oxygen radical absorbance capacity (ORAC) correlated neither to rosmarinic acid content nor to essential oil content. Total phenolic content (TPC) correlated moderately to rosmarinic acid content (r=0.39, n=352) as well as to essential oil content (r=0.25, n=352). The variation in antioxidant capacity can not be explained by the variation in the contents of rosmarinic acid or essential oil. The diversities in antioxidant capacity of oregano found in this study will allow a better plant exploitation for pharmaceutical uses and plant breeding of highly antioxidative genotypes of Origanum vulgare.