Garlic extract modulation of pulmonary vascular function: Comparisons among fresh, aged, freeze-dried powder and oil macerate

Garlic has been advocated for a variety of therapeutic applications including pulmonary vasodilation, but definitive experimental evidence supporting these claims remain inconclusive. We compared the relative vasorelaxation efficacy of fresh garlic extract (FG) to those commercially packaged garlics on rat pulmonary artery (PA) rings. Water extract of fresh whole garlic (1 - 500 μg/ ml) produced a dose-dependent relaxation in endothelium (EC)-mtact PA, reaching a maximum of -62±4% (M±SE of 18 rings). Maximum relaxation observed with the garlic storage leaves (-79±4%, n=16 rings) was significantly higher than the garlic inner stem (-48±5%, n=12 rings). Boiling of garlic extracts at 100°C for 30 mins reduced the relaxation by 10-20%. Mechanical disruption of EC or pretreatment with L-NAME, reduced the relaxation by 30-40% Extracts from freeze-dried powder (Garlique; Pure-Gar and Kwai), aged garlic (Garlique), and garlic oil macerate (Softgel) resulted in -87± 3% (n=16 rings), -72±6% (n=30 rings), -45±3% (n=30 rings), -22±5% (n=14 rings) and -5±3% (n=14 rings) relaxation, respectively. Vasoinhibitory effect of FG extract was readily reversible upon washing, whereas the Pure-Gar and Garlique effects tended to be longer lasting and PA contractile response remained depressed even after 60-min washing. These results show that extracts of both fresh and freeze-dried garlic, but not the oil macerate, are capable eliciting both EC-dependent and -independent relaxation in rat PA. Differences in vasorelaxant potency may be related to the concentrations of the garlic active ingredient, allicin, in different garlic preparations.