No abstract

In times of health crisis, including the current COVID‐19 pandemic, the potential benefit of botanical drugs and supplements emerges as a focus of attention, although controversial efficacy claims are rightly a concern. Phytotherapy has an established role in everyday self‐care and health care, but, since botanical preparations contain many chemical constituents rather than single compounds, challenges arise in demonstrating efficacy and safety. However, there is ample traditional, empirical, and clinical evidence that botanicals can offer some protection and alleviation of disease symptoms as well as promoting general well‐being. Newly emerging viral infections, specifically COVID‐19, represent a unique challenge in their novelty and absence of established antiviral treatment or immunization. We discuss here the roles and limitations of phytotherapy in helping to prevent and address viral infections, especially regarding their effects on immune response. Botanicals with a documented immunomodulatory, immunostimulatory, and antiinflammatory effects include adaptogens, Boswellia spp., Curcuma longa, Echinacea spp., Glycyrrhiza spp., medicinal fungi, Pelargonium sidoides, salicylate‐yielding herbs, and Sambucus spp. We further provide a clinical perspective on applications and safety of these herbs in prevention, onset, progression, and convalescence from respiratory viral infections.

Astaxanthin (AX)‐containing preparations are increasingly popular as health food supplements. Evaluating the maximum safe daily intake of AX is important when setting dose levels for these products and currently, there are discrepancies in recommendations by different regulatory authorities. We have therefore conducted a review of approved dose levels, clinical trials of natural AX, and toxicological studies with natural and synthetic AX. Recommended or approved doses varied in different countries and ranged between 2 and 24 mg. We reviewed 87 human studies, none of which found safety concerns with natural AX supplementation, 35 with doses ≥12 mg/day. An acceptable daily intake (ADI) of 2 mg as recently proposed by European Food Safety Authority was based on a toxicological study in rats using synthetic AX. However, synthetically produced AX is chemically different from natural AX, so results with synthetic AX should not be used in assessing natural AX safety. In addition, few safety studies have been conducted in either humans or animals with synthetic AX. We therefore recommend the ADI for natural AX to be based only on studies conducted with natural AX and further studies to be conducted with synthetic AX (including human clinical trials) to establish a separate ADI for synthetic AX.

The aim of our review is to demonstrate the potential of herbal preparations, specifically adaptogens for prevention and treatment of respiratory infections, as well as convalescence, specifically through supporting a challenged immune system, increasing resistance to viral infection, inhibiting severe inflammatory progression, and driving effective recovery. The evidence from pre-clinical and clinical studies with Andrographis paniculata, Eleutherococcus senticosus, Glycyrrhiza spp., Panax spp., Rhodiola rosea, Schisandra chinensis, Withania somnifera, their combination products and melatonin suggests that adaptogens can be useful in prophylaxis and treatment of viral infections at all stages of progression of inflammation as well as in aiding recovery of the organism by (i) modulating innate and adaptive immunity, (ii) anti-inflammatory activity, (iii) detoxification and repair of oxidative stress-induced damage in compromised cells, (iv) direct antiviral effects of inhibiting viral docking or replication, and (v) improving quality of life during convalescence.