Based on information from Salk Institute I have been using Fisetin and it has been reducing my phlegm significantly.  They recommended Doctors Best brand because they "know the source".  I started with 100 mg with meals morning and night.  It cleared out bacteria in the phlegm.  Only get phlegm about 1/2 hour after meals, and rest of day and night are great.  Much less phlegm when I do get some.