Methanolic leaf and root extracts of the Hawaiian kava (Piper methysticum Forst.) cultivars, Mahakea, Nene, Purple Moi and PNG, were tested on binding affinities to CNS receptors including GABAA (GABA and benzodiazepine binding site), dopamine D2, opioid (mu and delta), serotonin (5-HT6 and 5-HT7) and histamine (H1 and H2). HPLC analysis was carried out in order to determine the amount of the main kavalactones kavain, 7,8-dihydrokavain, methysticin, 7,8-dihydromethysticin, yangonin and 5,6-demethoxyyangonin. The most potent binding inhibition was observed for leaf extracts to GABAA receptors (GABA binding site) with IC50 values of approximately 3 micrograms/ml, whereas root extracts were less active with IC50 values ranging from 5 micrograms/ml (Nene) to 87 micrograms/ml (Mahakea). Since the leaf extracts generally contained lower amounts of the kavalactones than the root extracts, there might exist additional substances responsible for these activities. Leaf extracts also inhibited binding to dopamine D2, opioid (mu and delta) and histamine (H1 and H2) receptors more potently than the corresponding root extracts with IC50 values ranging from 1 to 100 micrograms/ml vs. > or = 100 micrograms/l, respectively. Significant differences in the potential of binding inhibition were also observed between cultivars. Binding to serotonin (5-HT6 and 5-HT7) and benzodiazepine receptors was only weakly inhibited by both root and leaf extracts of all four cultivars. In conclusion, our investigation indicates that the GABAA, dopamine D2, opioid (mu and delta) and histamine (H1 and H2) receptors might be involved in the pharmacological action of kava extracts. Since the cultivars contained similar amounts of kavalactones, while their pharmacological activities differed markedly, other constituents may play a role in the observed activities. Additionally, leaves generally exhibited more potent binding inhibition than roots, therefore leaf of P. methysticum might be an interesting subject for further pharmacological studies.

The aim of this project was to establish RAPD markers to determine the percentage of sexual off-spring of the facultative apomictic plant species H. perforatum. We did reciprocal crosses between four different accessions (A x B, B x A, C x D, D x C) by mechanical emasculation and hand pollination. Genomic DNA of the parents and the off-spring was isolated and PCR conditions were optimized in order to obtain reproducible bands with RAPD markers. Of the 260 screened RAPD primers 127 revealed polymorphism between the parental lines of A and B, whereas 53 revealed no amplification products. Each progeny was tested for the presence of paternal bands with three primers. We found no sexual off-spring among the 22 progenies of A x B, the nine progenies of B x A and the ten progenies of D x C. However, we detected six sexual off-spring among the 45 progenies of C x D. We have proved that RAPD markers can be used to distinguish between sexual and apomictic off-spring in H. perforatum and that sexual off-spring can be obtained from intraspecific crosses. The percentage of sexual progeny might depend on the genotype of the parental lines.