How many trials has not been done and how few have reached us!! Who is going to look into them?

QUEBRACHO Aspidosperma quebracho-bianco N.O. Apocynaceæ Synonyms. Quebracho Bark. Quebracho-bianco Part Used. Bark Habitat. Chile and Argentina, Bolivia, Southern Brazil

Medicinal Action and Uses. Tonic, febrifuge and anti-asthmatic. When a preparation of Quebracho or Aspidosperma is injected into the circulation, the rate and depth of the respiration increases largely, apparently apparently due to direct action on the respiratory centre, and the blood-pressure falls. Aspidosperma is used in medicine for the relief of various types of dyspnoea, especially in emphysema and in asthma. It is not generally useful to interrupt the paroxysm, but, as a rule, if used continuously, it will reduce the frequency and severity of attacks.

Grieve, Margaret. A Modern Herbal, Vol. II: 2 . Dover Publications. Kindle Edition. Nearly 100 years ago published, an exceptional source of traditional herbs

ARBOX, a molecular blend of quebracho and chestnut tannins extract and Vit B12, in patients affected by COVID-19.

https://pubmed.ncbi.nlm.nih.gov/33910614/