Due to the observational nature of the research, these results can’t be used to claim that specific flavonoids actually reduce the risk of coronary heart disease. This kind of claim requires randomized controlled trials, and there are no trials that test the isolated effect of these flavonoids on the risk of CHD. However, several meta-analyses of clinical trials have demonstrated that most of these flavonoids can improve intermediate risk factors for CHD:

A 2021 meta-analysis found that proanthocyanidins reduced blood pressure.^[2]
A 2017 meta-analysis found that flavonols lowered blood pressure and fasting glucose and increased HDL.^[3]
A 2018 meta-analysis found that anthocyanins lowered LDL and ApoB and increased HDL,^[4] and a 2020 meta-analysis found that anthocyanins reduced the inflammatory markers CRP, IL-6, and TNF-α.^[5]
Isoflavones were found to lower blood pressure in people with hypertension in a 2012 meta-analysis^[6] and improve arterial stiffness in a 2021 meta-analysis^[7].
Flavones have not been the subject of nearly as much clinical research as other flavonoids in terms of their effect on cardiovascular risk factors.

While the present study is observational and caution is warranted when interpreting these results, the fact that previous RCTs show positive changes to risk factors following supplementation with proanthocyanidins, flavonols, anthocyanins, and isoflavones does lend some credence to the possibility that there may be some casual relationship between these flavonoids (flavones excluded) and a reduced risk of CHD.

Evaluating the association between different types of flavonoids and coronary heart disease Original paper