Fungal Biofilms as a Valuable Target for the Discovery of Natural Products That Cope with the Resistance of Medically Important Fungi—Latest Findings

The development of new antifungal agents that target biofilms is an urgent need. Natural products, mainly from the plant kingdom, represent an invaluable source of these entities. The present review provides an update (2017–May 2021) on the available information on essential oils, propolis, extracts from plants, algae, lichens and microorganisms, compounds from different natural sources and nanosystems containing natural products with the capacity to in vitro or in vivo modulate fungal biofilms. The search yielded 42 articles; seven involved essential oils, two Brazilian propolis, six plant extracts and one of each, extracts from lichens and algae/cyanobacteria. Twenty articles deal with the antibiofilm effect of pure natural compounds, with 10 of them including studies of the mechanism of action and five dealing with natural compounds included in nanosystems. Thirty-seven manuscripts evaluated Candida spp. biofilms and two tested Fusarium and Cryptococcus spp. Only one manuscript involved Aspergillus fumigatus. From the data presented here, it is clear that the search of natural products with activity against fungal biofilms has been a highly active area of research in recent years. However, it also reveals the necessity of deepening the studies by (i) evaluating the effect of natural products on biofilms formed by the newly emerged and worrisome health-care associated fungi, C. auris, as well as on other non-albicans Candida spp., Cryptococcus sp. and filamentous fungi; (ii) elucidating the mechanisms of action of the most active natural products; (iii) increasing the in vivo testing.

Experimental Evidence for Therapeutic Potentials of Propolis

Propolis is produced by honeybees from materials collected from plants they visit. It is a resinous material having mixtures of wax and bee enzymes. Propolis is also known as bee glue and used by bees as a building material in their hives, for blocking holes and cracks, repairing the combs and strengthening their thin borders. It has been extensively used since ancient times for different purposes in traditional human healthcare practices. The quality and composition of propolis depend on its geographic location, climatic zone and local flora. The New Zealand and Brazilian green propolis are the two main kinds that have been extensively studied in recent years. Their bioactive components have been found to possess a variety of therapeutic potentials. It was found that Brazilian green propolis improves the cognitive functions of mild cognitive impairments in patients living at high altitude and protects them from neurodegenerative damage through its antioxidant properties. It possesses artepillin C (ARC) as the key component, also known to possess anticancer potential. The New Zealand propolis contains caffeic acid phenethyl ester (CAPE) as the main bioactive with multiple therapeutic potentials. Our lab performed in vitro and in vivo assays on the extracts prepared from New Zealand and Brazilian propolis and their active ingredients. We provided experimental evidence that these extracts possess anticancer, antistress and hypoxia-modulating activities. Furthermore, their conjugation with γCD proved to be more effective. In the present review, we portray the experimental evidence showing that propolis has the potential to be a candidate drug for different ailments and improve the quality of life.

Double-blinded randomized controlled trial to reveal the effects of Brazilian propolis intake on rheumatoid arthritis disease activity index; BeeDAI

Background and aims Brazilian propolis reportedly contributed to suppressing disease activity in a mouse model of rheumatoid arthritis (RA), suggesting new treatment options using Brazilian propolis. However, only results from animal experiments have been available, and the suppressive effects of Brazilian propolis on disease activity in humans with RA remain unknown. The purpose of this study was to clinically validate how Brazilian propolis intake changes disease activity in RA patients. Methods This study was conducted as a multicenter, double-blinded, randomized, placebo-controlled, parallel-group study of 80 women with RA (median age, 61.5 years; interquartile range, 56.0 to 67.3 years) showing moderate disease activity on Disease Activity Score in 28 joints using erythrocyte sedimentation rate (DAS28-ESR). Test tablets containing Brazilian propolis were used in Group P (40 patients), and Brazilian propolis-free placebo tablets were used as control in Group C (40 patients). Group P received 5 tablets of propolis (508.5 mg of propolis) daily, and Group C received 5 tablets of placebo daily. The intervention lasted 24 weeks, with change in DAS28-ESR set as the primary endpoint. As secondary endpoints, other disease activity assessment (DAS28 using C-reactive protein, simplified disease activity index, clinical disease activity index), ultrasonographic evaluation of synovitis, activities of daily living, quality of life, changes in cytokine levels, and adverse events over the course of the study were also assessed. Data were statistically analyzed by analysis of covariance. Results No significant differences in the primary endpoint were identified between groups (Group P vs Group C, effect: 0.14, 95% confidence interval: -0.21 to 0.49, p = 0.427). Likewise, no significant differences were seen between groups for any secondary endpoints. The adverse event rate during the study period was 28% in Group P and 33% in Group C. Conclusions Brazilian propolis exerted no effects on disease activity in patients with RA.

Alleviation of collagen-induced arthritis through cytokine-modulatory activity of Brazilian propolis AF-08 in mice

Brazilian propolis AF-08 as a dietary supplement has been shown to be effective in alleviating symptoms of herpes simplex virus and respiratory syncytial virus infection in mice. The alleviation was associated with the modification of immunological activity by AF-08 as a cytokine regulator. The immunomodulatory activity of AF-08 was suggested to contribute to the severity of symptoms and pathogenesis in cytokine-mediated diseases. In this study, we investigated the effectiveness of AF-08 as a potential cytokine modulator in alleviating autoimmune diseases. The efficacy and cytokine-modulatory activity of AF-08 were examined in collagen-induced arthritis (CIA) in mice. Mice were immunized with type II collagen. AF-08 at 0, 30, or 100 mg/kg was administered orally to the immunized mice once daily for three weeks before and/or three times daily for two weeks after the onset of CIA. The development of arthritis of the paws and inflammatory cytokine levels in serum were examined. AF-08 at 100 mg/kg significantly reduced the incidence and severity of CIA prophylactically and therapeutically and reduced the rise of systemic interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α levels in the early phase of CIA. In the early phase of CIA, the reduction of inflammatory cytokine levels by AF-08 correlated with the amelioration of symptoms of CIA. AF-08 might inhibit the initiation of cytokine-mediated disease rather than suppressing disease progression without toxicity. AF-08 was confirmed to possess cytokine-modulatory activity in vivo. It is possible that AF-08 is a potential prophylactic and therapeutic agent for autoimmune diseases.

Antifungal activity of green and red Brazilian propolis extracts

Background: Diseases associated to Candida spp. are recurrent and can be difficult to treat, mainly due to the new strains resistant to the limited number of available antifungals. Objective: Evaluate the in vitro and in vivo activity of Brazilian green propolis (GrProp) and red propolis (RdProp) ethanolic extracts against standard strains of Candida albicans, C. tropicalis, C. krusei, C. glabrata, C. parapsilosis and 10 clinical isolates of C. albicans. Methods: Antifungal activity in vitro was tested using the M-27-A3/CLSI protocol. The in vivo antifungal activity was evaluated using Tenebrio molitor model. And, the effect of extracts on adhesion of C. albicans in human buccal epithelial cells (BECs) was also studied. Results: GrProp and RdProp exhibited antifungal activity against at least one of the Candida strains tested. The adhesion inhibition of C. albicans in BECs was of 45% (GrProp28), 60% (GrProp50) and of 82% (RdProp), in comparison to amphotericin B (82%). All propolis extracts showed synergistic activity with fluconazole and amphotericin B. GrProp50 (10 mg/kg) showed the better protection of T. molitor, blocking the progression of C. albicans infection, increasing survival and delayed the larvae death. Conclusion: Brazilian GrProp and RdProp extracts inhibit the in vitro C. albicans growth and protect T. molitor against infection by this yeast. The physiochemical parameters found for the analyzed samples were in accordance to the standards established by the Brazilian Legislation for propolis and derivatives. GrProp and RdProp have potential to be used against Candida spp. infections, mainly in association with fluconazole or amphotericin B.