KUMERAHOU: Bronchial agent

Posted: April 2022
Author: Phil Rasmussen | M.Pharm., M.P.S., Dip. Herb. Med.; M.N.I.M.H.(UK),  F.N.Z.A.M.H. 

Kumerahou (Pomaderris kumerahou) is a branching shrub that only grows in the top half of the North Island of Aotearoa.  Its name probably derives from the fact that when its attractive creamy yellow flowers appear in the late winter or early spring, it was nature’s reminder to Māori that the kumara planting season had arrived. 

This native plant was highly esteemed by northern Māori, and its healing reputation extended to other regions of Aotearoa where it also became sought after. It was used as a remedy for a wide range of human ailments by Māori and then European migrants. Key applications included as a tonic for the kidneys and for rheumatic conditions, and a soap substitute for kauri gum diggers (‘gum diggers soap’ being its common name), bushmen and others. ^1-3

One of the most popular uses for preparations made from the leaves or leaves and flowers of kumerahou was for the treatment of various conditions affecting the lungs.

Many early reports mention its popularity as an alleged remedy for coughs and colds and bronchitis.^1-3 Upper respiratory tract infections including those from influenza had a serious toll on Māori communities after Europeans first landed on our shores, due to there being little immunity. This combined with poor living conditions and the absence of hospital care, meant that progression to the more serious bronchitis was relatively common. During these times there was a high degree of dependence on Rongoa Māori and traditional plant medicines such as kumerahou. Boil ups or decoctions were made usually from the dried leaves, then drunk at regular intervals. It was also sometimes combined with other herbs such as mingimingi (Cyathodes spp), kawakawa, koromiko, karamu or kohekohe.

Tuberculosis, a notoriously difficult to treat and very protracted infection that often caused permanent debility or death, was also treated with kumerahou. With tuberculosis still causing more than 2 million deaths annually and increasingly antibiotic-resistant forms emerging, this application of kumerahou warrants further investigation.

Since the 1930’s, kumerahou was also used to treat asthma, in doses sometimes higher than those taken for chest infections. Again, back then there were very few treatment options for this condition. Given the rather alarming incidence of asthma in Aotearoa today, and our dependence on steroid and adrenergic drug treatments, further investigations should take place into the potential role for kumerahou in the management of this condition.

Kumerahou has a rich content of saponins, as is observed when shaking a good quality kumerahou liquid preparation and watching the foam appear.  These are almost certainly contributory to its efficacy as an expectorant, anti-inflammatory and antimicrobial in treating these bronchial conditions.  Many saponin-rich plants are widely used as expectorants for chest infections, including such herbs as liquorice (Glycyrrhiza glabra), mullein (Verbascum thapsus) and senega (Polygala senega). An expectorant action by Kumerahou, in which the cilia of the respiratory tract are further encouraged to repel and eliminate unwanted microbes, allergens or particulate matter, strengthening their ability to help prevent the entry of airborne bacteria and viruses, probably underlines much of kumerahou’s value when treating respiratory tract infections.

Other potentially useful constituents for chest conditions found in the leaves and flowers of kumerahou include flavonoids such as quercetin and kaempferol. Quercetin is attracting increasing interest as a potential antiviral, due to its ability to inhibit or protect against the initial stages of virus infection and reduce inflammation caused by infection.^4-8 The astringency of its tannins, may also be helpful in a defensive effect against microbes.

While to date there is no published research on the potential antiviral properties of kumerahou, given its highly revered traditional and historical applications, and recent anecdotal reports of it being used with good outcomes as part of the overall treatment and management of various emerging microbial pathogens affecting our respiratory tracts, it warrants more attention in today’s world.  At the very least, it seems to have pronounced anti-inflammatory and strengthening effects on overall lung function, which combined with its expectorant effects, make it a powerful herb. Whilst its bitter and characteristically (some say notoriously) acrid flavour means patient compliance should be considered before prescribing, it combines well with liquorice and peppermint, and can be highly effective in helping to shift stubborn and intransigent infections of the respiratory tract.

References:

1. Brooker SG, Cambie RC, Cooper RC. New Zealand Medicinal Plants. Heinemann Publishers, Auckland, 1981.
2. Riley M., “Maori Healing and Herbal: New Zealand Ethnobotanical Sourcebook”, Viking Sevenseas, Paraparaumu, N.Z., 1994.
3. Rasmussen PL, Herbal Monograph: Kumerahou (Pomaderris kumerahou; P elliptica). Phytonews 2, Phytomed Medicinal Herbs Ltd, Auckland, New Zealand, Jan 1999.
4. Theoharides TC. Could SARS-CoV-2 Spike Protein Be Responsible for Long-COVID Syndrome? Mol Neurobiol. 2022 Mar;59(3):1850-1861.
5. Di Petrillo A, Orrù G, Fais A, Fantini MC. Quercetin and its derivates as antiviral potentials: A comprehensive review. Phytother Res. 2022 Jan;36(1):266-278.
6. Mbikay M, Chrétien M. Isoquercetin as an Anti-Covid-19 Medication: A Potential to Realize. Front Pharmacol. 2022 Mar 2;13:830205.
7. Manjunath SH, Thimmulappa RK. Antiviral, immunomodulatory, and anticoagulant effects of quercetin and its derivatives: Potential role in prevention and management of COVID-19. J Pharm Anal. 2022 Feb;12(1):29-34.
8. Shohan M, Nashibi R, Mahmoudian-Sani MR, Abolnezhadian F, Ghafourian M, Alavi SM, Sharhani A, Khodadadi A. The therapeutic efficacy of quercetin in combination with antiviral drugs in hospitalized COVID-19 patients: A randomized controlled trial. Eur J Pharmacol. 2022 Jan 5;914:174615. doi: 10.1016/j.ejphar.2021.174615. Epub 2021 Dec 2. PMID: 34863994; PMCID: PMC8638148.