The chapter describes the isolation and identification of phenolic substances from cockroach oothecae. Veratric acid was isolated from Blatta orientalis oothecae through a series of chemical treatments, including extraction, concentration, and recrystallization. The isolated acid was identified by its melting point and further characterized by converting it to its acid chloride and anilide. Protocatechuic acid was also isolated from the same oothecae by a different method, involving evaporation and recrystallization. The total yield of veratric acid was 426 mg. The phenolic substance present in cockroach oothecae was identified as protocatechuic acid (3:4-dihydroxybenzoic acid). The chapter discusses the spectrophotometric determination of tyrosine and tryptophan in proteins. It outlines the selective absorption of protein solutions in the ultraviolet region, particularly at wavelengths near 280 nm. The method involves analyzing binary systems using intensities of absorption at selected wavelengths, with a focus on the contributions from tyrosine and tryptophan. The procedure is validated through experiments with various protein solutions, demonstrating its accuracy and reproducibility. The method is particularly useful for analyzing small amounts of proteins and can handle a wide range of concentrations, provided that irrelevant absorption is correctly corrected. The chapter also discusses the limitations of the method, such as the need for precise instrumental settings and the impact of extreme molar ratios on accuracy. Overall, the method is shown to be effective for analyzing tyrosine and tryptophan in proteins with high accuracy and speed.The chapter describes the isolation and identification of phenolic substances from cockroach oothecae. Veratric acid was isolated from Blatta orientalis oothecae through a series of chemical treatments, including extraction, concentration, and recrystallization. The isolated acid was identified by its melting point and further characterized by converting it to its acid chloride and anilide. Protocatechuic acid was also isolated from the same oothecae by a different method, involving evaporation and recrystallization. The total yield of veratric acid was 426 mg. The phenolic substance present in cockroach oothecae was identified as protocatechuic acid (3:4-dihydroxybenzoic acid). The chapter discusses the spectrophotometric determination of tyrosine and tryptophan in proteins. It outlines the selective absorption of protein solutions in the ultraviolet region, particularly at wavelengths near 280 nm. The method involves analyzing binary systems using intensities of absorption at selected wavelengths, with a focus on the contributions from tyrosine and tryptophan. The procedure is validated through experiments with various protein solutions, demonstrating its accuracy and reproducibility. The method is particularly useful for analyzing small amounts of proteins and can handle a wide range of concentrations, provided that irrelevant absorption is correctly corrected. The chapter also discusses the limitations of the method, such as the need for precise instrumental settings and the impact of extreme molar ratios on accuracy. Overall, the method is shown to be effective for analyzing tyrosine and tryptophan in proteins with high accuracy and speed.