β-carotene, a member of the carotenoid family, is a provitamin A, and can be converted into vitamin A (retinol), which plays essential roles in the regulation of physiological functions in animal bodies. Microalgae synthesize a variety of carotenoids including β-carotene and are a rich source of natural β-carotene. This has attracted the attention of researchers in academia and the biotech industry. Methods to enrich or purify β-carotene from microalgae have been investigated, and experiments to understand the biological functions of microalgae products containing β-carotene have been conducted. To better understand the use of microalgae to produce β-carotene and other carotenoids, we have searched PubMed in August 2021 for the recent studies that are focused on microalgae carotenoid content, the extraction methods to produce β-carotene from microalgae, and the bioactivities of β-carotene from microalgae. Articles published in peer-reviewed scientific journals were identified, screened, and summarized here. So far, various types and amounts of carotenoids have been identified and extracted in different types of microalgae. Diverse methods have been developed overtime to extract β-carotene efficiently and practically from microalgae for mass production. It appears that methods have been developed to simplify the steps and extract β-carotene directly and efficiently. Multiple studies have shown that extracts or whole organism of microalgae containing β-carotene have activities to promote lifespan in lab animals and reduce oxidative stress in culture cells, etc. Nevertheless, more studies are warranted to study the health benefits and functional mechanisms of β-carotene in these microalgae extracts, which may benefit human and animal health in the future.

Gentianaceae herb extracts have been widely used as food additives, teas or medicinal remedies for various diseases and disorders of the human body. Herein, the potential effects of iridoids, seco-iridoids and analog glycosides from gentian on acontine-induced hepatotoxicity were investigated in HepG2 cells to obtain metabolic data of drug-biotarget interactions. Molecular docking analysis was performed to assess the binding efficiencies of 53 iridoids, seco-iridoids and analog compounds obtained from 50 gentian species to the active sites of human CYP3A4 enzyme. The docking scores of 29 iridoids, seco-iridoids and 24 analog glycosides were calculated from the free energy of ligand–protein complexes using a computer-assisted docking simulation. After comprehensive evaluation, 6 of these compounds, i.e., gentiopicroside, sweroside, swertiamarin, loganic acid, 6-O-β-D-glucosyl-gentiopicroside and amarogentin were selected to evaluate their hepatoprotective effects. Quantitative real-time PCR was used to measure the expression levels of CYP3A4 mRNA in HepG2 cells. Amarogentin displayed the most clear inductive effect on CYP3A4 mRNA levels in the HepG2 cells. Moreover, amarogentin was further studied for acontine-induced toxicity in the HepG2 cells to determine the potential mechanisms. Amarogentin displayed obvious inductive effect on CYP3A4 mRNA levels in the HepG2 cells. These results elucidated that the hepatoprotective effects were caused by the facilitation of drug metabolism, amelioration of mitochondrial dysfunction and reduction of oxidative stress. Our data demonstrated that the naturally found iridoids, seco-iridoids and analog glycosides in gentian may be responsible for the hepatoprotective effects of gentian-extracted compounds and thus, this study may be useful in the food industry or in clinical practice.

Aconitine is the main bioactive ingredient of Aconitum plants, which are well-known botanical herbs in China. Aconitine is also notorious for its high cardiotoxicity, as it can induce life-threatening ventricular arrhythmias. Unfortunately, there are few effective antidotes to aconitine toxicity. This study aimed to evaluate the potent protective effects of the ingredients from V. baillonii on aconitine toxicity on H9c2 cell line. Cell viability was assessed by methylthiazoltetrazolium bromide (MTT). Intracellular Ca²⁺ concentration alteration and reactive oxygen species (ROS) generation were observed by confocal microscopy and flow cytometry, respectively. Cellular oxidative stress was analyzed by measuring malondialdehyde (MDA) and superoxide dismutase (SOD) levels. Mitochondrial membrane potential (ΔΨ) was determined using JC-1 kit. RT-PCR and Hoechst staining techniques were conducted to determine the levels of autophagy/apoptosis. The mRNA levels of dihydropyridine receptor (DHPR), ryanodine receptors (RyR2) and sarcoplasmic reticulum Ca²⁺-ATPase (SERCA) were measured by RT-PCR. We screened six components from V. baillonii, among which, sweroside exhibited the strongest protective effects on aconitine-induced cardiac toxicity. Sweroside suppressed the aconitine-induced mRNA expressions of Na_V1.5 (encoded by SCN5A), RyR2 and DHPR, and reversed the aconitine-induced decrease in mRNA level of SERCA, thus preventing the aconitine-induced persistent intracellular Ca²⁺ accumulation and avoiding intracellular Ca²⁺ overload. We further found that sweroside restabilized the aconitine-disrupted mitochondrial membrane potential (ΔΨ) and reversed the aconitine-induced increase in the mRNA levels of cell autophagy-related factors (Beclin-1, Caspase-3, and LC3- II) in H9c2 cells. In the whole-animal experiments, we observed that sweroside (50 mg/kg) alleviated effectively aconitine-induced arrhythmias by analysis of electrocardiogram (ECG) recording in rats. Our results demonstrate that sweroside may protect cardiomyocytes from aconitine toxicity by maintaining intracellular Ca²⁺ homeostasis, restabilizing mitochondrial membrane potential (ΔΨ) and avoiding cell autophagy/apoptosis.

Novel antibacterial carbon dots (CDs), because of their excellent biocompatibility, biological activity, and advantages in imaging, have been a hot spot in recent studies. This paper reports the simple and fast preparation of multifunctional blue-emitting protamine sulfate (PS)-derived CDs (PS-CDs) through a one-step microwave-assisted method. The prepared PS-CDs exhibit advantages such as excellent water solubility, low cell toxicity and excellent blood compatibility. The minimum inhibitory concentration (MIC) test was used to systematically study the antimicrobial efficacy of the prepared PS-CDs against various microorganisms, including Gram-positive and Gram-negative bacteria and fungi. The produced PS-CDs exhibit strong antibacterial activity against Staphylococcus aureus (S. aureus) with a MIC of 25 μg mL⁻¹ and methicillin-resistant S. aureus (MRSA) with a MIC of 37.5 μg mL⁻¹. Additionally, PS-CDs show little difference in their sensitivity to S. aureus and drug-resistant bacteria but high sensitivity to the structural differences of Gram-negative bacteria. In addition, the antibacterial mechanism of these PS-CDs is proposed, and the application of these PS-CDs for imaging was realized, thanks to their easy internalization into bacteria. Compared to traditional antibacterial agents, both the bactericidal activity and biological imaging of PS-CDs demonstrate their high potential for applications in the biomedical field.

This paper reports the formation process and fluorescence mechanism of synthetic carbon dots using citric acid, N-acetyl-l-cysteine and glutathione derivatives as carbon sources.