RESUMEN
Absent in the wild, Tahitian vanilla (V. tahitensis) is a gourmet spice restricted in distribution to cultivated and feral stands in French Polynesia and Papua New Guinea. Its origins have been elusive. Our objective was to test the purported hybrid derivation and parentage of V. tahitensis from aromatic, neotropical progenitors. Nucleotide sequences from V. tahitensis and neotropical Vanilla were assayed for phylogenetic relatedness in two independently inherited genomic regions, the nuclear ITS region, and the trnH-psbA noncoding region of chloroplast DNA. As predicted to occur for early generation hybrids, placement of V. tahitensis was nonconcordant. All V. tahitensis clustered with V. planifolia from analysis of cpDNA sequences, suggesting V. planifolia as the maternal genome contributor. Phylogenetic reconstruction of ITS sequences showed that most V. tahitensis nested incongruently with V. odorata, but others remained sister to V. planifolia. Recovery of ITS clones in V. tahitensis related to both V. planifolia and V. odorata also supports its biphyletic origin from these two taxa. We interpret the high percentage (95%) of additive polymorphic sites in V. tahitensis relative to its parents as indication of a recent, and probably human-mediated, evolutionary origin.
RESUMEN
The allelochemical potential of Callicarpa acuminata (Verbenaceae) was investigated by using a biodirected fractionation study as part of a long-term project to search for bioactive compounds among the rich biodiversity of plant communities in the Ecological Reserve El Eden, Quintana Roo, Mexico. Aqueous leachate, chloroform-methanol extract, and chromatographic fractions of the leaves of C. acuminata inhibited the root growth of test plants (23-70%). Some of these treatments caused a moderate inhibition of the radial growth of two phytopathogenic fungi, Helminthosporium longirostratum and Alternaria solani (18-31%). The chloroform-methanol (1:1) extract prepared from the leaves rendered five compounds: isopimaric acid (1), a mixture of two diterpenols [sandaracopimaradien-19-ol (3) and akhdarenol (4)], alpha-amyrin (5), and the flavone salvigenin (6)]. The phytotoxicity exhibited by several fractions and the full extract almost disappeared when pure compounds were evaluated on the test plants, suggesting a synergistic or additive effect. Compounds (4), (5), and the semisynthetic derivative isopimaric acid methyl ether (2) had antifeedant effects on Leptinotarsa decemlineata. Compound 5 was most toxic to this insect, followed by (2), (4), and (6) with moderate to low toxicity. No correlation was found between antifeedant and toxic effects on this insect, suggesting that different modes of action were involved. All the test compounds were cytotoxic to insect Sf9 cells while (6), (4), and (1) also affected mammalian Chinese Hamster Ovary (CHO) cells. Compound 5 showed the strongest selectivity against insect cells. This study contributes to the knowledge of the defensive chemistry and added value of C. acuminata.
