Lichens are an important source of phenolic compounds and have been intensively investigated for their biological and pharmacological activities. Lecanoric acid (1), a lichen depside, was isolated from a Parmotrema tinctorum specimen and treated with alcohols to produce orsellinic acid (2) and orsellinates (3) to (9) (2,4-dihydroxy-6-n-methyl benzoates). Free radical scavenging activity of methyl (3), ethyl (4), n-propyl (5), n-butyl (6), iso-propyl (7), sec-butyl (8), tert-butyl (9) orsellinates was evaluated using 2,2′-diphenyl-1-picrylhydrazyl (DPPH) method. Results showed that chain elongation of methyl (3) to n-butyl (6) causes a rise in the antioxidant activity. However, iso-propyl (7) and tert-butyl (9) were more active than the correspondent linear compounds, although sec-butyl (8) was less active among the chain ramified compounds. All the orsellinates were less active than lecanoric acid (1) and orsellinic acid (2). Orcinol (10) and resorcinol (11) were also determined for comparison with activities of orsellinates. Gallic acid (12) was used as control.
地衣是
酚类化合物的重要来源,人们对其
生物和药理活性进行了深入研究。从 Parmotrema tinctorum 标本中分离出地衣苷酸 Lecanoric acid (1),并用醇处理生成 orsellinic acid (2) 和 orsellinates (3) 至 (9)(2,4-二羟基-6-正甲基
苯甲酸酯)。采用 2,2′
-二苯基-1-苦基
肼(
DPPH)法评估了
橙皮苷酸甲酯(3)、
乙酯(4)、正
丙酯(5)、正丁酯(6)、异
丙酯(7)、仲丁酯(8)和叔丁酯(9)的自由基清除活性。结果表明,甲基(3)链延长为正丁基(6)会导致抗氧化活性上升。不过,异丙基(7)和叔丁基(9)的活性高于相应的线性化合物,但仲丁基(8)的活性在链延伸化合物中较低。所有
橙皮苷酸的活性都低于
柠檬酸(1)和
橙皮苷酸(2)。此外,还测定了 Orcinol (10) 和 resorcinol (11),以便与 orsellinates 的活性进行比较。
没食子酸(12)用作对照。