Fruits, immunity and COVID

Medicinal plants along with their secondary metabolites are used as complementary medicine to treat a wide range of diseases. Inflammatory conditions include a wide range of diseases like rheumatic and immune-mediated conditions, diabetes, cardiovascular accident, and etcetera. Some herbs like Curcuma longa, Zingiber officinale, Rosmarinus officinalis, Borago officinalis, evening primrose, and Devil’s claw possesses anti-inflammatory effects which have been evaluated in clinical and experimental studies.  

Curcuma longa

Curcumin is the most important secondary metabolite of C. longa, which is responsible for the anti-inflammatory effect of this plant.

Many clinical trials have proven curcumin to be effective in improving inflammation of rheumatoid arthritis (RA) and reducing the clinical manifestation of RA, such as joint swelling and morning stiffness. It has also proven to be beneficial in irritable bowel syndrome (IBS) treatment. Additionally, it acts as a reducing agent to delayed graft rejection (DGR) after kidney transplant surgery. It benefits ulcerative colitis and psoriasis by the selective prohibition of phosphorylase kinase.

Zingiber officinale

Long-term consumption of Z. officinale extract has shown to increase the serum corticosterone level and reduce pro-inflammatory markers. It uses in type 2 diabetic patients with low-grade inflammation, after 2 months of treatment, showed decreased serum level of TNF-α and high-sensitivity C-reactive protein (hs-CRP). It has also greatly benefitted patients with osteoarthritis. The ginger powder shows improvement in musculoskeletal and rheumatism patients by inhibiting cyclooxygenase and lipoxygenase pathway in synovial fluid.

Rosmarinus officinalis

Rosemary extract has been shown to decrease hs-CRP noticeably in patients with osteoarthritis (OA), rheumatoid arthritis (RA), and fibromyalgia. Evidence proves that rosmarinic acid can disturb complement system activation easily by inhibiting C3b attachment, in a very low dose. It has also shown gastroprotective action against gastric ulcers by inhibiting neutrophils infiltration and reducing pro-inflammatory mediators: TNF-α and IL-1. 

It has additionally demonstrated topical anti-inflammatory effect wound healing in mice. 

Borago officinalis

This plant contains gamma-linolenic acid (GLA), which is a strong suppressor of TNF-α. GLA elevates prostaglandin-E (PGE) level causing cyclic adenosine monophosphate (cAMP) augmentation and is responsible for the anti-inflammatory effect of borage oil in rheumatoid arthritis (RA). 

The anti-inflammatory effect of borage oil has also been tested and proved beneficial in patients with atopic dermatitis. 

Oenothera biennis (Evening Primrose)

Evening primrose oil contains active components as GLA, linear aliphatic alcohols (e.g., Tetracosanol), and phenolic compound (ferulic acid) which shows protective roles against proinflammatory markers. 

It also contains sterols like β-Sitosterol and Campesterol that possess a modulator effect on nitric oxide (NO), TNF-α, IL-1β, and thromboxane B2 (TXB2) which leads to suppression of COX-2 gene expression. Evening primrose oil has shown its effectiveness in patients with multiple sclerosis (MS) by significantly reducing IFN- and IL-17 levels. 

Harpagophytum procumbens (Devil’s Claw)

H. procumbens contains Harpagoside as the chief anti-inflammatory component. Devil’s claw root extract possesses inhibition potential of NO, inflammatory cytokines (IL-6, IL-1β, and TNF-α), and PGE2, prevention of arachidonic acid metabolism and eicosanoid biosynthesis causing COX-2 inhibition and reducing inflammation. Devil’s claw has also shown anti-inflammatory effects in osteoarthritis.

Boswellia serrata

Boswellia serrata extract has shown dramatic alleviation in the frequency of joint swelling and pain and augmentation in joint flexibility and walking distance in patients with osteoarthritis. it also causes a significant reduction in erythrocyte sedimentation rate (ESR), morning stiffness, and NSAID requirement in rheumatoid arthritis patients. 

B. serrata has proven clinically effective in ameliorating Collagenous colitis, an inflammatory bowel disease (IBD). B. serrata  Combined with C. longa and Glycyrrhiza glabra has been shown to reduce the symptoms in the asthmatic patient’s symptoms; by significantly diminishing plasma levels of leukotriene C4 (LTC4), NO, and malondialdehyde. 

B. serrata extract has proven its inflammatory mediators modulating properties both in vivo and in vitro.

Rosa canina

Rosehip has demonstrated alleviation in pain, rescue medication consumption, and stiffness and a significant reduction in CRP in patients with OA. Similarly, it has demonstrated a reduction in ESR and improvement in the quality of life in RA patients. 

n-hexane and dichloromethane extracts of rosehip inhibit COX-1, COX-2, and LTB4, and also are a rich source of unsaturated fatty acids. Additionally, Galactolipid is an active component in rosehip powder with NO inhibitory potential.

Urtica dioica

The topical effectiveness of nettle leaf has been demonstrated in osteoarthritis of the thumb by significantly alleviating pain, stiffness, and anti-inflammatory and analgesic therapy requirements. The combination of nettle leaf with rosehip and willow bark has been shown to suppress IL-1β and COX-2 in chondrocytes and have chondroprotective and anti-inflammatory effects.

It also shows anti-inflammatory potential in allergic rhinitis by antagonizing the H1-receptor, reducing PGD2 production (allergy specific prostaglandin), and inhibiting mast cell tryptase.

Persea americana/Glycine max

Avocado/soybean unsaponifiables (ASU) have demonstrated a reduction in Lequesne’s functional index (LFI), pain, and disability; lessened the requirement of NSAID in patients with OA.

it has also demonstrated beneficial effects in patients with linear scleroderma and morphea by preventing atrophy, deformity, and contracture. Topical and dietary administrations of Avocado and soybean extract have also shown positive effects in mild to moderate vulvar lichen sclerosus (VLS). 

Elaeagnus angustifolia

The effectiveness of Oleaster has been demonstrated in the treatment of oral lichen planus (OLP) lesions. It has shown significant attenuation in TNF-α and matrix metalloprotein-1 (MMP-1) (proinflammatory mediators) and alleviation in IL-10 (an anti-inflammatory cytokine) in patients with OA.

Its aqueous extract has shown anti-inflammatory properties in mice through COX-1 and COX-2 inhibition.

Vaccinium myrtillus

Bilberry diminishes hs-CRP, IL-6, and IL-12 and circulating LPS concentration. 

Olea europaea

Extra virgin olive oil (EVOO) has a positive effect on modulating postprandial plasma lipopolysaccharide, proinflammatory cytokines, TXB2 and LTB4, and has a diminished performance in risk of coronary heart disease. 

Conclusion-

Curcuma longa holds the greatest clinical evidence of its use in different inflammatory disorders like RA, uveitis, and IBD. Additionally, other listed herbs have also demonstrated good performance in clinical and experimental anti-inflammatory tests. 

Biochemical studies have clearly shown the potential role of herbs in the activation or inhibition of proinflammatory cytokines, although more clinical studies with larger participants and meta-analyses are warranted. There exists a large variety of herbs that possess anti-inflammatory effects, but evaluating them all is out of the scope of this letter.

Ghasemian M, Owlia S, Owlia MB. "Review of Anti-Inflammatory Herbal Medicines", Advances in Pharmacological and Pharmaceutical Sciences, 2016;2015.