Isoflavone profiles in different plant parts of red clover

Red clover (Trifolium pratense L., Fabaceae) is important source of isoflavones, among which the most present are: daidzein, genistein, formononetin and biochanin A [1]. These substances are considered to be beneficial for reduction of menopausal symptoms, prevention of osteoporosis, cancer and cardiovascular diseases. Since red clover extracts are used for production of dietary supplements, it is important to evaluate profile of these active compounds in plant parts. The aim of this study was to determine content of daidzein, genistein, formononetin and biochanin A in different plant parts of red clover, and to investigate which isoflavone is present in highest concentration.

Stems, leaves and flowers of five red clover cultivars were grounded and mixed with water 30 minutes on 37°C. After that, 3M HCl and 96% ethanol were added and mixture was heated to boiling. Extracts were than purified by solid phase extraction on HLB cartridges. Isoflavones were identified and quantified in samples by high-performance liquid chromatography (HPLC), using corresponding standard compounds [2].

Total isoflavone content was on average the highest in leaves (2,73mg/g), and the lowest in stems of red clover cultivars (0,47mg/g). Isoflavone content in flowers varied between 0.53–1.05mg/g. In leaves formononetin was dominant (1,62mg/g), while the lowest average content had biochanin A in stems (0,04mg/g). The highest individual concentrations of all investigated isoflavones were found in leaves of different cultivars. On average, in all analyzed samples formononetin was the most present isoflavone.

References: 1. Sivesind E, Seguin P (2005)J Agric Food Chem 53: 6397–6402.

2. Krenn L et al. (2002)J Chromatogr B 777:123–128.