Obtenção de derivados de compostos isolados de Zingiber officinale por biotransformação e semi-síntese e avaliação frente à cisteinil-proteases
Abstract
Several aromatic polyketide derivatives from Ginger (Zingiber officinale), like zingerone,
6-gingerol and 6-shogaol were obtained by biocatalytic reactions and semi-synthesis and
both their antifungal and cysteine-proteinase inhibitory properties were investigated. The
derivatives obtained by semi-synthesis were evaluated in the form of a first screening for
inhibition property of growth of phytopathogenic fungi Colletotrichum gloesporioides and
Fusararium oxysparum. The biotransformation of four compounds: zingerone purchased
from Sigma Aldrich, 6-gingerol isolated from ginger and its derivatives 4-methyl-6-gingerol
and 6-shogaol was investigated using whole cells of C. gloesporioides and showed
recognition of the fungal pool of enzymes capable of using such compounds as substrates.
All experiments were conducted in sterile liquid medium BD (Potato and Dextrose) under
agitation (120 rpm) and constant temperature (30° C ), obtaining the methanol extract of
mycelial mass (MM), the aqueous extract (Aq) and the ethyl acetate extract (Ac) of culture
fluid. The ethyl acetate extract was analyzed by GC-MS and ESI-MS/MS using LC-MS
techniques. The fungus C. gloesporioides proved able to promote a reaction of aromatic
oxidative coupling of zingerone, forming a dimer of this molecule. This product was
isolated, identified by NMR spectroscopy and high resolution mass spectrometry. The
biotransformation experiment was also made with isotopically labeled zingerone with
deuterium. Analysis of the ethyl acetate extract (Ac) by (-) ESI-MS / MS using LC-IT-MS
showed that dimer formation since the first day once the isotopically labeled fragments
were detected. The aromatic oxidative coupling reaction also occurs in the
biotransformation to phenolic compound 6-gingerol by C. gloesporioides. It is probable that
side chain of 6-gingerol was used as carbon source forming an alcohol with molecular
mass 168 Da. The dimer of the alcohol appears as biotransformation product. Among the
proposed semi-synthesis reactions, the insertion of an oxime ether subunit from zingerone
as starting material was obtained. Despite the molecular modeling indicates good
complementarity with the catalytic site model cysteinyl preoteases, the product obtained
does not show inhibitory activity against the enzymes L and V to 25 uM. The oximine
derivative of 8-gingerol, presented halo of inhibition against the proliferation of fungus
C.gloesporioides in disk diffusion test on PDA (Potato Dextrose Agar) in a Petri dish. The
ethyl acetate extract (Ac) from the tenth day showed a good result of inhibition of cathepsin
V (80%). There are studies that investigate the relationship between the antifungal activity
of compounds of the property of inhibiting cysteine-preoteases as papain and cathepsin B
and L.