Abstract: The total alkaloid content in the cydonia. Mill was assayed by using spectrophotometer by way of bromophenol blue for testing acid dyes. When the total alkaloid formed stable complex compound with bromophenol blue. The alkaloid content in the cydonia oblonga Mill was first time assayed as about 1.4%. This method could be considered as quick, simple method with higha ccuracy.

Key words: cydonia oblonga Mill, total biological alkali, bromophenol blue colorimetry