Different ratio of plant extract to salt solutions could be used. Plant extracts vs salt solution can be used 50:50 to 10:90. If your selected plants are rich in polyphenolic compounds then it will work even 5:95.
There is no fixed ratio as it will be highly dependent upon the concentration of extract itself. As a starting point, you can take equimolar solution of extract and salt solution.
Different ratio of plant extract to salt solutions could be used. Plant extracts vs salt solution can be used 50:50 to 10:90. If your selected plants are rich in polyphenolic compounds then it will work even 5:95.