Oleos essenciais de Baccharis e sua interação com insetos polinizadores

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

Correlation among Baccharis species revealed the essential oils similarity of B. dracunculifolia, B. erioclada. B. caprariaefolia. B. platipoda, B. tridentata, B. vincaefolia and B. myriocephala. From a daytime monitoring of B. dracunculifolia male and female plants we could observe that the inflorescences are mainly responsible for the mono/sesquiterpene ratio variation with a noticeable inversion occurring al about 11:00 AM. This phenomenom was associated to the pollinator attration based on field observations and correlation analyses between volatiles and visiting insects leading the final conclusion that the solitary bees Augochoropsi cupreola and Paroxystoglossa jocasta are responsible for B.dracunculifolia polination in our region. Monoterpenes alcohols (like terpineol and geraniol) are the allelochemicals responsible for the insect behaviour and pollination. Several synthetic standards were obtained (10-metoxy-4-hydroxy-aromadendrane 24c, epoxy-calarene 23a, hidroxy-a-gurjunene,21b, epoxy-a-copaene 19a and 19b, epoxy-a-cubebene 18a and a-guaiene 40a) and coinjected in B. caprariaefolia, B. myriocephala, B. tridentata, B. platipoda, B.erioclada, B. dracunculifolia and B. vincaefolia. None of them were detected in the volatile components of these plants. Three novel cadinanes, axial-cadinol 41, 1b,6b,-diol 45 and 6a,7a-epoxide 46 were detected and identified in B. platipoda and B. tridentata. Another cadinane derivative was detected but was not fully characterized in B. myriocephala and B. tridentata. Nor-taylorione 66 was obtained in an efficient synthesis envolving a Pauson- Khand reaction in the Iast step. Its presence was not confirmed in the essential oils of the studied Baccharis species but it was detected in the volatiles components of Artemisia annua. This compound is a novel sesquiterpene possessing a novel skeleton. Nor-taylorione 66 synthetic pathway is one of the few examples of Pauson-Khand reaction application to the synthesis of natural product.

ASSUNTO(S)

polinização monoterpenos sesquiterpenos

ACESSO AO ARTIGO

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