The aim of this study is the determination of some chemical properties of black and white fruits of Myrtus communis growing wild in Tunisia. Berries were collected from North West of Tunisia. Different treatments were applied to myrtle fruits: fruits without treatment, fruits soaked in water for one night, fruits soaked in water for two nights, fruits boiled in water and fruits boiled in water and soaked for one night. The obtained juices from berries were collected stored at 4°C for further analysis. Titratable Acidity (TA) and pH were measured. The total phenols content was determined by Folin Ciocalteu method, the total flavonoid content of juice was determined by the aluminium chloride colorimetric method and the total condensed tannin content was determined by vanillin method. The antioxidant capacity of the studied samples was determined applying the DPPH assay. Statistical analysis of acidity showed high significant differences between the two types of fruits and between treatments. Analysis of total polyphenols content showed significant differences between the five studied treatments. Myrtle black berries contained highest amount of flavonoids when compared with white fruits. Untreated berries showed the lowest amount of flavonoids (0.57 mg RE/mL of juice). The lowest amount of condensed tannins was reached by fruits soaked in water for two nights (128.08 mg CE/mL and 233.72 mg CE/mL respectively for black and white berries) while untreated fruits showed the highest values. No significant differences were recorded for the antioxidant activity.