Studies on the Anticandidal Mode of Action of Allium sativum (Garlic)

Abstract

The mode of action of aqueous garlic extract (AGE) was studied in Candida albicans. The minimum inhibitory concentration (MIC) of AGE against six clinical yeast isolates ranged between 0.8 and 1.6 mg ml-I. Scanning electron microscopy and cell leakage studies showed that garlic treatment affected the structure and integrity of the outer surface of the yeast cells. Growth of C . albicans in the presence of AGE affected the yeast lipid in a number of ways : the total lipid content was decreased ; garlic-grown yeasts had a higher level of phosphatidylserines and a lower level of phosphatidylcholines; in addition to free sterols and sterol esters, C. albicans accumulated esterified steryl glycosides; the concentration of palmitic acid (16 : 0) and oleic acid (18 : 1) increased and that of linoleic acid (18 : 2) and linolenic acid (18 : 3) decreased. Oxygen consumption of AGE-treated C. albicans was also reduced. The anticandidal activity of AGE was antagonized by thiols such as L-cysteine, glutathione and 2-mercaptoethanol. Interaction studies between AGE and thiols included growth antagonism, enzymic inhibition and interference of two linear zones of inhibition. All three approaches suggest that AGE exerts its effect by the oxidation of thiol groups present in the essential proteins, causing inactivation of enzymes and subsequent microbial growth inhibition.

Antibacterial mode of action of <i>Ginkgo biloba</i> leaf essential oil: Effect on morphology and membrane permeability

“…Previously such morphological alterations have been observed for various kinds of test organisms when treated with different essential oils (Zhu et al, 2005;Bajpai et al, 2009). These morphological alterations in bacterial cells might be occurred due to the effect of G. biloba leaf essential oil on membrane integrity, thereby resulting in the lysis of bacterial cell wall followed by the loss of intracellular dense material on the surface of treated cells, as evident by the previous findings (Ghannoum, 1988). Changes in membrane fluidity are usually occur due to alterations in membrane lipid composition (Sikkema et al, 1994) and are thought to be a compensatory mechanism to counter the lipid disordering effects of the treatment agent.…”

Antimycotic potential of a diterpenoid taxoquinone against <i>Candida</i> species isolated from <i>Metasequoia glyptostroboides</i>

“…These altered morphological features might be occurred due to the detrimental effect on membrane integrity, thereby resulting in the lysis of Candida cell wall followed by the loss of intracellular dense material of treated cells, similar findings were also confirmed by others (Ghannoum, 1988;Wang et al, 2005). Although the putative mechanism of action is not clear but it might be assumed from the above results that the anticandial effect of the taxoquinone could be attributed due to its effect on cell wall synthesis, enzymes inhibition, leakage of cellular material and ergosterol biosynthesis.…”

Paracoccidioides brasiliensis by ajoene is associated with blockade of phosphatidylcholine biosynthesis

“…Ajoene is an inhibitor of in vitro growth of P. brasiliensis al., 1988), it seems highly selective for the fungal membrane where it modifies the headgroup composition of P. brasiliensis phospholipids, similar to the effect of aqueous garlic extracts (AGE) on C. albicans (Adetumbi et al, 1986;Ghannoum, 1988) tion of the SFA/UFA ratio was observed in M cultures when ajoene was added to them.…”