Hepatocytes Detoxify Atuna racemosa Extract

Antimicrobial Secondary Metabolites from the Mangrove Plants of Asia and the Pacific

Microbes such as the White Spot Syndrome Virus account for severe losses in the shrimp farming industry globally. This review examines the literature on the mangrove plants of Asia and the Pacific with antibacterial, antifungal, or antiviral activities. All of the available data published on this subject were collected from Google Scholar, PubMed, Science Direct, Web of Science, ChemSpider, PubChem, and a library search from 1968 to 2022. Out of about 286 plant species, 119 exhibited antimicrobial effects, and a total of 114 antimicrobial natural products have been identified including 12 with MIC values below 1 µg/mL. Most of these plants are medicinal. The mangrove plants of Asia and the Pacific yield secondary metabolites with the potential to mitigate infectious diseases in shrimp aquaculture.

A randomized Phase I study of Atuna racemosa: a potential new anti-MRSA natural product extract

AIM

We previously reported significant antimicrobial activity against Gram-positive bacteria from the extract of the Atun tree (Atuna racemosa), identified through rapid digital bioprospecting of a 400-year-old historic herbal text. Toxicity studies in human cell lines showing safety, combined with the ethnomedical descriptions of botanical use, suggested that this extract might be clinically useful against topical Gram-positive bacteria infections.

MATERIALS AND METHODS

Using a minimal inhibitory concentration assay, we examined the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) to an extract of the kernel of the Atun tree (Atuna racemosa). Additionally, a maximum tolerated topical application of the extract was determined in a randomized, double-blind, placebo-controlled pilot clinical trial.

RESULTS

Here we report that the effectiveness of this Atuna racemosa extract against MRSA (MIC=16-32microg/mL) is on par with currently available last-line antibiotics, while it remains well tolerated in short-term topical applications of 10 times the minimally inhibitory concentration.

CONCLUSIONS

Although further studies are needed to determine safety and clinical efficacy, this effective extract, identified in a 400-year-old historic herbal text, may prove to be clinically useful in the treatment of MRSA.

Aloin induces apoptosis in Jurkat cells

Aloe is widely used as a dietary supplement. However, there are continuing concerns over the toxicity and the purity of aloe-based products. The primary class of compounds responsible for aloe-induced toxicity are anthraquinones. One of these, aloe-emodin, has been extensively investigated for apoptosis inducing effects. Conversely, the precursor to aloe-emodin, aloin, has been subjected to only minimal investigation of any cytotoxic effects. Jurkat T cells, an established model for the study of compound toxicity, were used to evaluate the effect of aloin on cell viability. Cells were analyzed using flow cytometry and microscopy for cell size and granularity, cell membrane integrity, mitochondrial membrane potential, and cell cycle profile. Treatment with aloin resulted in a reduction in cell size, compromised membrane integrity, and loss of mitochondrial membrane potential in a dose-dependent manner. Additionally, treatment with aloin resulted in alteration of the cell cycle, specifically a block at G2/M phase. Importantly, the loss of cell membrane integrity was preceded by a loss of mitochondrial membrane potential, suggesting a mitochondrial-dependent pathway for aloin-induced apoptosis. These observations provide insight into the potential mechanisms of aloin-induced toxicity and thus, perhaps, aloe preparation-induced toxicity. Furthermore, because of the concern over the safety of aloe-based supplements, this work suggests that aloe supplements not containing aloin may be safer than aloe supplements containing aloin, and that aloin should be considered in addition to concentrations of aloe-emodin.

Antibacterial properties and toxicity of Atuna racemosa extract depend on kernel maturity

Through data mining a historic herbal text, we identified Atuna racemosa-Raf. as a plant with alleged antibacterial properties. We have shown that these purported antibacterial properties are most prominent in the kernel of the nut of the plant. While working with traditional healers in Samoa during a botanical collection trip, we identified a range of maturity stages of the kernel. Here we show that the antibacterial properties are different at different stages of kernel maturity, and that the immature kernels have a lower minimal inhibitory concentration (MIC) than the mature kernels. Additionally, we show there is a negative correlation between the antibacterial properties and cytotoxic properties (a stronger antibiotic is less cytotoxic), suggesting there are two separate compounds with disparate characteristics. These findings have implications for the use of this natural product as an antibiotic and chemotherapeutic agent.

A high-throughput cell-based toxicity analysis of drug metabolites using flow cytometry

The effects of liver enzymes on drug activities are important considerations in the drug discovery process. Frequently, liver microsomes are used to simulate first-pass metabolism in the liver; however, there are significant disadvantages to the microsome system. As an alternative, a simple cell-based, high-throughput system that allows for examination of metabolite activity is described. Using multiparameter flow cytometry and the low-volume, high-sample format of 96-well plates, it is possible to rapidly evaluate a dose-response curve for metabolites based on variables including initial compound concentrations, hepatocyte cell line metabolic activities, and time. Using HepG2 cells as a surrogate for hepatic metabolism of a potential therapeutic, the impact of metabolites on Jurkat cell death was measured by both propidium iodide dye exclusion and cell cycle analysis. While this system is not proposed to supplant liver microsome studies, this alternative assay provides a highly adaptable, low-cost, and high-throughput measure of drug metabolism.

A high-throughput 3-parameter flow cytometry-based cell death assay

Apoptosis plays a role in many disease states, and the evaluation of novel therapeutics that alters the apoptotic cascade is an area of intense investigation. However, many generally available methods to evaluate cell death are either time consuming, imprecise, or both. We report a system that permits simultaneous evaluation of three apoptotic markers (cell membrane integrity, mitochondrial membrane potential, and cell cycle progression) with minimal technical manipulation. This system is particularly well-suited for toxicologic evaluation of novel compounds and profiling of new apoptosis-inducing agents.