**2.9. Lignan and their cytotoxic activities**

Lignans based on (C6-C3)2 biphenolic skeleton and they consists on a large group of plant phenolic produced by the oxidative dimerization of two phenyl propanoid moieties. They are found in black berries, strawbwerries, raspberries, blue berries, broccoli, apricot, cabbage and many seeds. The antiestrogenic effects of lignans could help to reduce the risk of hormoneassociated breast, uterine, ovarian and prostate cancers.

Pinoresinol, boehmenan and boehmenan H were found the most cytotoxic against human cancer cell lines Lu1, LNCaP and MCF-7 and a normal cell line HUVEC with ED50 values for Lu1 cell line was 0.8, 10.4 and 5.3 g mL−1, for LNCaP cell line was 0.5, 9.5 and 7.7 g mL−1, while the ED50 values for MCF-7 cell line was 1.7, 10.0 and 10.2 g mL−1, ED50 values for HUVEC 1.1, 9.0 and 6.2 g mL−1 were observed for these lignans. The cytotoxic activity of pinoresinol against various cancer cell lines has been mentioned in the literature. It exhibited cytotoxicity against the KB cell line with an IC50 value of 2.2 μg mL−1 [90]. The cytotoxic activity of Sambucasinol A, B and C was evaluated by determining their inhibitory effects on human tumor cell lines A549, SK-OV-3, SK-MEL-2 and XF498 using the SRB bioassay. These compounds showed cytotoxicity against all cell lines, with IC50 values in the range of 11.07–19.62 μM [89]. The IC50 values for the pycnanthulignene A ranged from 0.20 μM (towards CCRF-CEM cells) for pycnanthulignene A to 195.12 μM (towards CEM/ADR5000 cells) for doxorubicin [41]. Phyllanthusmin C showed significant cytotoxicity against human leukemia HL-60 cells, human breast MCF-7 cells and human colon SW480 cell lines with IC50 values of 9.2, 19.2 and 20.5 μM, compared with the cisplatin with IC50 values of 1.7, 10.9 and 9.9 μM, respectively [92] (**Figure 8**).

**Figure 7.** Structure of phenanthrenes **96**–**99**.

Phenolic Compounds from the Natural Sources and Their Cytotoxicity http://dx.doi.org/10.5772/66898 51

**Figure 8.** Structure of lignans **100**–**107**.

**Figure 7.** Structure of phenanthrenes **96**–**99**.

50 Phenolic Compounds - Natural Sources, Importance and Applications
