There have been some clinical studies suggesting that the consumption of hibiscus tea may lower blood pressure, but the papers published about these studies note that the quality of the studies is poor.[8][9] Hibiscus tea is generally well tolerated and does not adversely affect liver and kidney function at lower doses, but it may be hepatotoxic at high doses.[9] Hibiscus flowers contain anthocyanins, which are believed to be the active antihypertensive compounds, acting as angiotensin-converting enzyme (ACE) inhibitors.