Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.
Department of Life and Environmental Sciences, University of Cagliari, 09124, Cagliari, Italy.
BMC Complement Altern Med. 2019 Apr 5;19(1):82. doi: 10.1186/s12906-019-2487-7.
Cytinus is small genus of endophytic parasitic plants distributed in South Africa, Madagascar, and in the Mediterranean region. In the latter area, two species occur, Cytinus hypocistis and C. ruber, distinguished by both morphological characters and ecological traits. We characterized the ethanolic and aqueous extracts obtained from the inflorescences of C. hypocistis and C. ruber collected in Sardinia, Italy, and explored their tannin content, antioxidant properties and antimicrobial activities.
Total phenolic contents were determined by Folin-Ciocalteu spectrophotometric method. Tannin content was determined by HPLC. Antioxidant activity of the extracts was tested with both electron transfer-based (FRAP, TEAC, DPPH) and spectrophotometric HAT methods (ORAC-PYR). The antimicrobial activities of extracts/compounds were evaluated using the broth microdilution method. The bactericidal activity was evaluated using the time-kill method. Biofilm formation was evaluated by crystal violet (CV) staining assay.
Characterization of the tannin profile of C. hypocistis and C. ruber revealed a significant amount of gallotannins, in particular 1-O-galloyl-β-D-glucose. In addition, pentagalloyl-O-β-D-glucose was present in all extracts, reaching the concentration of 0.117 g/kg in the ethanolic extract of C. hypocistis. C. hypocistis extracts displayed a strongest antioxidant activity than C. ruber extracts. Three Gram-positive bacterial species tested (Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecium) resulted sensitive to both Cytinus extracts, with MICs ranging from 125 to 500 μg/ml for aqueous extracts and from 31.25 to 250 μg/ml for ethanolic extracts; on the contrary, Gram-negative strains (Pseudomonas aeruginosa and Klebsiella pneumoniae) were not affected by Cytinus extracts. Intriguingly, we observed the suppressive activity of ethanolic extracts of C. hypocistis and C. ruber on biofilm formation of S. epidermidis. Experiments performed with synthetic compounds indicated that pentagalloyl-O-β-D-glucose is likely to be one of the active antimicrobial components of Cytinus extracts.
These findings show that Cytinus extracts have antimicrobial and antioxidant activities, suggesting a possible application of Cytinus as sources of natural antimicrobials and antioxidants.
Cytinus 是一种小型内生寄生植物，分布于南非、马达加斯加和地中海地区。在地中海地区，有两个物种，即 Cytinus hypocistis 和 C. ruber，它们在形态特征和生态特征上都有所不同。我们对采集自意大利撒丁岛的 C. hypocistis 和 C. ruber 花序的乙醇和水提取物进行了表征，并研究了它们的单宁含量、抗氧化特性和抗菌活性。
采用 Folin-Ciocalteu 分光光度法测定总酚含量。采用 HPLC 法测定单宁含量。采用电子转移法（FRAP、TEAC、DPPH）和分光光度法 HAT 法（ORAC-PYR）测定提取物的抗氧化活性。采用肉汤微量稀释法评价提取物/化合物的抗菌活性。采用时间杀伤法评价杀菌活性。采用结晶紫（CV）染色法评价生物膜形成。
对 C. hypocistis 和 C. ruber 中单宁谱的分析表明，存在大量的没食子单宁，特别是 1-O-没食子酰基-β-D-葡萄糖。此外，在所有提取物中都存在五没食子酰基-O-β-D-葡萄糖，在 C. hypocistis 的乙醇提取物中浓度达到 0.117g/kg。C. hypocistis 提取物的抗氧化活性强于 C. ruber 提取物。测试的三种革兰氏阳性菌（金黄色葡萄球菌、表皮葡萄球菌、粪肠球菌）对两种 Cytinus 提取物均敏感，水提物的 MIC 范围为 125-500μg/ml，乙醇提物的 MIC 范围为 31.25-250μg/ml；相反，革兰氏阴性菌（铜绿假单胞菌和肺炎克雷伯菌）不受 Cytinus 提取物的影响。有趣的是，我们观察到 C. hypocistis 和 C. ruber 的乙醇提取物对表皮葡萄球菌生物膜形成的抑制活性。用合成化合物进行的实验表明，五没食子酰基-O-β-D-葡萄糖可能是 Cytinus 提取物中具有抗菌活性的成分之一。
这些发现表明 Cytinus 提取物具有抗菌和抗氧化活性，提示 Cytinus 可能作为天然抗菌和抗氧化剂的来源得到应用。
