The plant species Arbutus unedo shows numerous beneficial pharmacological effects (antiseptic, antidiabetic, antidiarrheal, astringent, depurative, antioxidant, antihypertensive, antithrombotic, and anti-inflammatory). For the medicinal use, standardization of extracts is a necessity, as different compounds are responsible for different biological activities. In this paper, we analyze monthly changes in the content of quercitrin, isoquercitrin, hyperoside, and chlorogenic acid. Methanolic extracts of the leaves are analyzed by HPTLC for the identification and quantification of individual polyphenol, and DPPH test is used to determine antioxidant activity. Based on the results obtained, the leaves should be collected in January to obtain the highest concentrations of hyperoside and quercitrin (0.35？mg/g and 1.94？mg/g, resp.), in June, July, and October for chlorogenic acid (1.45–1.46？mg/g), and for the fraction of quercitrin and isoquercitrin in November (1.98？mg/g and 0.33？mg/g, resp.). Optimal months for the collection of leaves with the maximum recovery of individual polyphenol suggested in this work could direct the pharmacological usage of the polyvalent herbal drugs. 1. Introduction Arbutus unedo L. (Ericaceae, English strawberry tree) is an evergreen shrub or a small tree reaching up to 12？m in height. It is found mainly in European Mediterranean region growing in maquis, evergreen scrub, woodland margins, and on rocky slopes. The leaves of A. unedo are alternate, simple, oblanceolate, dark green, leathery, short-stalked, and toothed. The flowers are bell shaped, with recurved lobes, 8-9？mm long, white, often tinged with pink or green, and honey scented. The fruits are globose berries about 15–20？mm in diameter, ripening through yellow to scarlet and deep crimson. Since the fruits take about 12 months to ripen, a tree carries mature fruits and flowers at the same time, and the appearance of both during winter months also makes this plant very popular for specimen plantings [1, 2]. The leaves of A. unedo are used as a urinary antiseptic, antidiabetic, antidiarrheal, astringent, depurative, antioxidant, antihypertensive, antithrombotic, anti-inflammatory agent [3–8]. Chemical investigations of leaves and fruits show the presence of essential oil, flavonoids, proanthocyanidins, iridoid glucosides, sugars, nonvolatile and phenolic acids, vitamins C and E and carotenoids [9–13]. As a pharmacological activity can rarely be attributed to a group of compounds as it is the case with polyphenols and antioxidant activity, the identification and
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