Dear Elif Öztürk ,

that depends on what you want to know. Alkaloids is a general description, which tells you that there is a nitrogen in the molecule. Flavonoids is a description about the chemical skeleton of the compound, which always has multiple OH groups. Both alkaloids and flavonoids are biosynthesised from phenyl alanine or tyrosine (generally speaking, ther are a lot of alternative pathways!), so they may share a common biosynthetic pathway. In Solanaceous species, several classes of alkaloids can be found, such as tropane alkaloids and the solanidine aklaloids, which do originate from different precursors. As a first advice: define your question more accurate. It is strongly dependent upon plant species. Kind regards, Harrie Verhoeven

Dear Harrie A Verhoeven,

Firstly thank you for your precious feedbacks. I looked for structure of flavonoids and alkaloids. As i searched from literature, alcholoid content (Theobromine & caffeine) is not important level for searching all plant species but some plants (cocoa bean) is important to research because of toxic effects of alcholoids if they are consumed high amounts. But that kind of plants have the bioactive compounds such as flavonoids. Their basic chemical structure are the same.Are they only differed from each other with nitrogen and -OH groups. Does nitrogen group makes theobromine toxic chemical compound?. 

Yours Sincerely,

Elif ÖZTÜRK

Dear Filip Miljković,

Thank you for your attention and beneficial feedbacks,too. Then, we can't say flavonoids are always beneficial compounds for health. As it is indicated toxicology, their dose is important. 

Yours Sincerely,

Elif