Abietane diterpenoids from Salvia sclarea transformed roots as growth inhibitors of pathogenic Acanthamoeba spp

Effectiveness of phytoproducts against pathogenic free-living amoebae - A scoping and critical review paving the way toward plant-based pharmaceuticals

Infections caused by free-living amoebae (FLA) have increased worldwide and are expected to worsen. The lack of drugs that are effective (especially against cysts), affordable, and safe to treat these infections exacerbates the concern. Plants present a promising source of bioactive compounds for developing effective drugs; however, the scientific literature on this topic has yet to be adequately synthesized. This work provides a critical scoping review summarizing the amoebicidal performance of plant-derived products and their potential for developing effective drugs to treat FLA infections. Out of 5889 articles retrieved from multiple databases, 119 articles were selected, from which data on 180 plant species belonging to 127 genera and 62 families were extracted. The extracts, essential oils, and compounds from these plants exhibited a diverse range of potency against cysts and trophozoites. Among the compounds studied, periglaucine A, kolavenic acid, and (+)-elatol are promising cysticidal drug candidates due to their high potency, as well as their known low toxicity to non-target cells. Tovophillin A, gartinin, 8-deoxygartinin, garcinone E, 9-hydroxycalabaxanthone, γ-mangostin, and borneol also exhibit high cysticidal potency, but their selectivity profile is unknown. Resveratrol, rosmarinic acid, β-amyrin, and vanillic acid stand out for their high potency against trophozoites and low toxicity to mammalian cells. Another group of compounds with similarly high trophocidal potency includes (-)-epicatechin, (-)-epigallocatechin, apigenin, costunolide, demethoxycurcumin, kaempferol, methyl-β-orcinolcarboxylate, sakuraetin, (+)-elatol, debromolaurinterol, luteolin, (-)-rogiolol, cystomexicone B, epigallocatechin gallate, quercetin, and α-bisabolol. These compounds are priority candidates for further studies on in vivo efficacy, safety, pharmacokinetics, and pharmacodynamics.

Effect of Salvia officinalis and S. sclarea on rats with a high-fat hypercaloric diet

Phytotherapy for the correction of excess body weight is widely used. However, a comprehensive study of herbal preparations on the organism of model animals has been carried out only for a few plant species. Supplementing the diet of rats with closely related sage species (Salvia officinalis L. and S. sclarea L.) against the background of high-fat hypercaloric diet triggered multidirectional changes in their metabolism. The addition of crushed dry shoots of S. officinalis to the diet of animals led to a sharp increase in their body weight (up to 130.8% of the initial one in 30 days of the experiment). The body weight of the rats treated with S. sclarea for 30 days increased only up to 103.8% of their initial weight and was lower than in the control group. Addition of S. officinalis caused an increase in daily weight gain up to 253.1% of the control group, and S. sclarea – its decrease to 27.8% of the daily weight gain in the control group. In the S. officinalis group, the relative weight of the brain, spleen, and thymus decreased, while in the S. sclarea group, the relative weight of the thymus decreased and that of the colon increased. Under the influence of S. officinalis, the concentration of urea, total bilirubin, and triglycerides in the blood plasma of male rats decreased and the concentration of total protein and the activity of alkaline phosphatase increased. While consuming S. sclarea shoots, there was an increase of alkaline phosphatase activity in the rats’ blood, but atherogenic index (23.1% of the level of the control group) sharply dropped due to an increase in the concentration of high-density lipoprotein cholesterol (286.9% of the control) and a decrease in the concentration of low-density lipoprotein cholesterol (67.7% of control). In rats feeding on S. sclarea shoots, we observed a decrease in the concentration of triglycerides in the blood (39.9% of the control), a decrease in the activity of gamma-glutamyl transferase (62.8%), and an increase in the Ca/P ratio (132.5% of the control group). No significant changes were observed in CBC and WBC differential of male rats when eating S. officinalis and S. sclarea shoots. According to the results of the open field test, the physical and orientational activity of male rats under the influence of S. officinalis significantly decreased by the end of the experiment. Emotional status of rats, on the contrary, decreased when they ate dry crushed shoots of S. sclarea in the composition of the food. Thus, excess body weight of rats in the conditions of hypercaloric diet led to more pronounced deviations from the norm while consuming dry crushed shoots of S. officinalis. The addition of S. sclarea dry crushed shoots to the animals’ diet normalized the body weight in comparison with the control group, reduced the negative manifestations of obesity at the biochemical and organismal levels. In this regard, the substances that contains S. sclarea should be carefully studied for anti-atherosclerotic activity, and tea supplemented with S. sclarea shoots can be recommended as a corrective supplement in the diet of overweight people.

In vitro amoebicidal effect of Aloe vera ethanol extract and honey against Acanthamoeba spp. cysts

This study evaluated in vitro effect of different concentrations of Aloe vera (A. vera) ethanol extract and honey against Acanthamoeba spp. cysts in comparison with chlorhexidine (the drug of choice for treatment of Acanthamoeba infection) at different incubation periods. Four different concentrations of the tested agents were used, 100, 200, 400, and 600 μg/ml for A. vera ethanol extract and 25, 50, 100, and 200 μg/ml for honey. Isolated Acanthamoeba spp. cysts from keratitis patients were incubated with different concentrations of the tested agents as well as chlorhexidine 0.02% (drug control) for different incubation periods (24, 48, 72 h). After each incubation period, the effect of A. vera extract and honey against Acanthamoeba cysts was assessed by counting the number of viable cysts, determining the inhibitory percentage and detecting the morphological alternations of treated cysts compared to non-treated and drug controls. Both A. vera ethanol extract and honey showed a concentration and time-dependent effect on the viability of Acanthamoeba cysts. In comparison with chlorhexidine (the drug control), A. vera ethanol extract possessed a potent cysticidal activity at all tested concentrations throughout different incubation periods, except for concentration 100 μg/ml which recorded the lower inhibitory effect. With increasing the dose of A. vera ethanol extract to 200, 400, 600 µg/ml, the recorded inhibitory percentages of Acanthamoeba cysts viability were 82.3%, 92.9% and 97.9% respectively, after 72 h compared to 76.3% of chlorhexidine. Similarly, honey at concentrations of 50-100 µg/ml gave higher inhibitory effect of 59% and 76.7%, respectively compared to chlorhexidine which showed an inhibitory percentage of 55.7% after 24 h. Meanwhile, the lowest tested concentration of honey (25 µg/ml) gave an inhibitory effect by 47.7-67% which was less than that of chlorhexidine throughout different incubation periods. With increasing the dose of honey to 200 µg/ml, the inhibitory effect was 98.9% after 72 h higher than that of chlorhexidine (76.9%). Using a scanning electron microscope, Acanthamoeba cysts treated by A. vera ethanol extract showed alternations in their shapes with flattening, collapsing, and laceration of their walls. Also, treated cysts by honey were highly distorted and difficult to identify because most of them were shrinkage and collapsed to a tiny size. On the other hand, chlorhexidine showed less structural and morphological changes of Acanthamoeba cysts. A. vera ethanol extract and honey had considerable cysticidal effects on Acanthamoeba cysts. They may give promising results for treatment of Acanthamoeba keratitis.

Synthesis and in vitro activity of new biguanide-containing dendrimers on pathogenic isolates of Acanthamoeba polyphaga and Acanthamoeba griffini

The genus Acanthamoeba can cause Acanthamoeba keratitis (AK) and granulomatous amoebic encephalitis (GAE). The treatment of these illnesses is hampered by the existence of a resistance stage that many times causes infection relapses. In an attempt to add new agents to our chemotherapeutic arsenal against acanthamebiasis, two Acanthamoeba isolates were treated in vitro with newly synthesized biguanide dendrimers. Trophozoite viability analysis and ultrastructural studies showed that dendrimers prevent encystment by lysing the cellular membrane of the amoeba. Moreover, one of the dendrimers showed low toxicity when tested on mammalian cell cultures, which suggest that it might be eventually used as an amoebicidal drug or as a disinfection compound in contact lens solutions.

Acanthamoebicidal activity of periglaucine A and betulinic acid from Pericampylus glaucus (Lam.) Merr. in vitro

Acanthamoeba species are pathogenic protozoa which account for amoebic keratitis, conjunctivitis and granulomatous amoebic encephalitis. These amoebae form cysts which resist drugs and more effective acanthamoebicidal agents are needed. Medicinal plants could be useful in improving the current treatment strategies for Acanthamoeba infections. In the present study, we examined the amoebicidal effects of Pericampylus glaucus (Lam.) Merr., a medicinal plant used for the treatment of conjunctivitis in Malaysia. Pathogenic Acanthamoeba triangularis were isolated from environmental water samples and treated with different concentrations of fractions obtained from Pericampylus glaucus (Lam.) Merr. as well as main constituents for 24-72 h. Chlorhexidine was used as a reference drug. Ethanol fraction of stem showed significant (p < 0.05) inhibition of trophozoites survival. Betulinic acid and periglaucine A from this plant at 100 μg/mL inhibited more than 70% survival of both cysts and trophozoites. The calculated therapeutic index for betulinic acid and periglaucine A was 170 and 1.5 for trophozoites stage and 3.75 and 8.5 for cysts stage. The observed amoebicidal efficacies indicate the beneficial aspects of this plant in the treatment of Acanthamoeba infection. Periglaucine A could also be of value for the treatment of Acanthamoeba infection.

Artemisia annua L. as a plant with potential use in the treatment of acanthamoebiasis

The treatment of acanthamoebiasis is a great problem. Most cerebral invasions end with death, and the treatment of ocular invasions is usually long-lasting and not very effective. Numerous plant extracts and substances isolated from plants, which are effective against trophozoites or cysts, have been studied in the treatment of acanthamoebiasis. However, no agents that are simultaneously effective against both developing forms of amoebae have been discovered yet. It seems that such a plant which fulfils both tasks is Artemisia annua L. Our studies showed that water, alcohol and chloroform extracts from the herb A. annua L. can be applied in general and local treatment or in combined therapy with antibiotics in the treatment of acanthamoebiasis. Extracts from this plant show not only in vitro but also in vivo effects. Studies carried out on experimental animals infected with amoebae show that the application of these extracts significantly prolongs the survival of the animals.