Specific Plant Terpenoids and Lignoids Possess Potent Antiviral Activities against Severe Acute Respiratory Syndrome Coronavirus
Betulinic Acid is found in large concentrations in the bark of Birch Trees. Fungi which grows on dead or dying Birch Trees concentrate the acid and other potent medicinal compounds found in the trees into themselves. The main fungi which grow on Birch Trees include Chaga, Birch Polypore and Turkey Tail Mushroom, the Birch Bark can be used too as that is where the medicinal compounds are stored by the tree. Once you have obtained these you can concentrate them by making an extraction such as a Tincture, Dual Extraction Tincture or a Spagyric.
From the PDF –
The inhibitory properties of betulinic acid (13) and savinin (16) on the enzymatic activity of SARS-CoV 3CL protease. Protease enzyme activity was measured using 8-80 µM of fluorogenic substrate in the absence (b) or presence of 25 µM(0 and 50 µM(2) compound. The data were fitted with eq 1 using KINETASYST II program to calculate the Ki values of betulinic acid (13) and savinin (16). The inhibition pattern indicates that compounds 13 and 16 are competitive inhibitors with respect to the substrate.