Progênies de meios-irmãos de erva-baleeira (Varronia curassavica Jacq.) : extrato aquoso, óleo essencial, rebrota, colheita em duas épocas e atividadeantiprotozoária sobre Ichthyophthirius multifiliis

Abstract

The chemical diversity of the medicinal and aromatic species Varronia curassavica is exceptionally rich. The essential oil of the species contains (E)-caryophyllene and viridiflorol compounds, which confer strong antiprotozoal activity against Ichthyophthirius multifiliis, the causal agent of the so-called white spot disease in fish. This parasite reduces fish productivity and survival in environments of fish cultivation. Breeding is one of the main ways of developing aromatic plant cultivars with high contents of compounds of interest for industrial application and adapted to the climatic conditions of the country. In addition, the residual water obtained after extraction of essential oils by hydrodistillation can also be useful in controlling the above parasite. The objective of this study was therefore to establish and evaluate half-sib progenies of V. curassavica, to extract and evaluate the residual water (here called aqueous extract) from hydrodistillation of two accessions, and to assess the essential oil contents, regrowth, harvest in two seasons and antiprotozoal activity on I. multifiliis. Testing was carried out at the experimental farm Campus Rural of the Federal University of Sergipe (UFS) and on the premises of Embrapa Coastal Tablelands. The first assay evaluated the chemical composition and antiprotozoal activity of the aqueous extract obtained by hydrodistillation from V. curassavica accessions VCUR-202 and VCUR-503 on the protozoan I. multifiliis. The second experiment evaluated half-sib progenies grown from seeds harvested from plants of accession VCUR-503 (chemotype (E)-caryophyllene and viridiflorol). The morphoagronomic and chemical characteristics and antiprotozoal activity against I. multifiliis were evaluated in 88 halfsib progenies and the female parent (VCUR-503). In the third trial, the influence of the growing season (dry or rainy) on essential oil contents, production and chemical composition in the halfsib progenies was assessed. The aqueous extract from both V. curassavica accessions proved toxic to I. multifiliis, at a level of LC50 =150.46 mg.L-1 for VCUR-202 and 121.67 mg.L-1 for VCUR- 503 in trophons; and for the tomont phase at LC50=199.63 mg.L-1 for VCUR-202 and 122.65 mg.L-1 for VCUR-503. Morphological cluster analysis indicated the presence of two morphologically distinct groups. Of the half-sib progenies, 71% had higher essential oil contents than parent VCUR-503. Chemical cluster analysis formed two groups, of which group II comprised 22 half-sib progenies with high means of α-pinene (7.92%), (E)-caryophyllene (7.77%) and viridiflorol (46.74%). Progenies with viridiflorol contents between 42.41% and 64.74% induced protozoan mortality between 35% and 72%, at a viridiflorol concentration of 10 mg.L-1 . Interestingly, the progeny with the highest viridiflorol content did not cause the highest protozoan mortality. In addition to (E)-caryophyllene, other compounds can act synergistically with viridiflorol, while compounds such as α-pinene and germacrene D can act antagonistically, reducing the antiprotozoal activity of the essential oil. Two chemical groups were also observed in both growing seasons of the half-sib progenies: Group I, rich in α-pinene and (E)-caryophyllene and Group II, with α-pinene, (E)-caryophyllene and viridiflorol. Higher essential oil contents were produced by parent VCUR-503 and 14 half-sib progenies in the dry season. In the mean, higher contents of compound (E)-caryophyllene were produced in the rainy and of viridiflorol in the dry season.