Anti-Proliferative Activity of Launaea fragilis (Asso) Pau and Launaea nudicaulis (L.) Hook.F. Extracts Anti-Proliferative Activity of

Wild medicinal plants are an efficient source of anticancer agents. The widely distributed Launaea fragilis and Launaea nudicaulis in Egypt were investigated for their anti-proliferative activities against some cancer cell lines. Ethanol extracts of the two species were evaluated in vitro by Sulforhodamine B (SRB) assay on six cell lines; hepatocellular carcinoma (Hep G2), prostatic carcinoma (PC-3), colorectal carcinoma (HCT116), non-small cell lung carcinoma (H1299), breast adenocarcinoma (MCF7) and colon adenocarcinoma (Caco-2). The results showed that the incubation of both L. fragilis and L. nudicaulis with non-small cell lung carcinoma (H1299) inhibited significantly the cell proliferation with IC 50 =26.5 and 20 µg/ml, respectively. Launaea fragilis recorded the lowest inhibition values for prostatic carcinoma (PC-3) with IC 50 =40µg/ml. However, breast adenocarcinoma (MCF7) revealed the lowest inhibition value for L. nudicaulis with IC 50 =35µg/ml. Ethanol extract of L. nudicaulis was more effective in the inhibition of the cell proliferation than that of L. fragilis for the six cell


Background
Cancer is a rapid division of abnormal cells which grow beyond their normal limits. Similarly, it can attack adjacent parts of the body and spread to other organs. Lung and breast are the most common cancers (2.09 million cases) followed by colorectal, prostate, skin and stomach in a decreasing order. According to the World Health Organization [1], cancer is the second prominent reason of death globally and it is responsible for an estimated 9.6 million deaths in 2018 and approximately 70% of mortality occurs in the poor developing countries. Chemotherapeutic agents of cancer possessed toxic side effects on patients, as the cardiac, pulmonary, neurological and renal toxicity, besides to their limited anticancer activities which impeded the conquering of this disease [2,3]. Nowadays, there is an increasing demand to discover new anticancer agents that are more selective and less toxic than those currently used [4]. The natural metabolites acted as a repository of various bioactive compounds, which considered a valuable source of anticancer agents [3,5,6]. Launaea Cass. (Asteraceae, Cichorioideae, Cichorieae) is polymorphic and controversial genus with confused intraspecific delimitation. It comprised about 54 species and 10 subspecies distributed in different geographical regions [7]. It had economic values, ecological and ethnobotanical importance [8][9][10]. Despite the richness of Launaea species with different phenolic compounds such as flavonoids, coumarins and terpenoids [11][12][13][14], only limited data was available concerning the anticancer effects of its members.
This study aimed to assess the anti-proliferative activities of L.  Kilian [7] and Boulos [15] at the latter herbarium.

Anti-Proliferative Assay
A pooled sample was prepared for each species from their aerial parts. Ten grams of powdered sample was macerated in 95% ethanol (100 ml) for 24 hours at room temperature. The solution was filtered, and the filtrate was evaporated. Extracts were tested at the National Cancer Institute, Cairo, Egypt, by serial subcultures according to Skehan et al. [16]. Surviving fractions of cells throughout extract exposure was characterized graphically by IC50 values. IC50 values were estimated by a linear least-squares regression of the growth values versus the logarithm of the extract concentration; only concentrations that yielded growth values between 10% and 90% were used in the calculation. A bar parallel to the x-axis and intersecting the point 50% on the y-axis was constructed. Also, a bar was plotted parallel to the y-axis that starts from the point of intersection of the bar with the dose-response plot. Therefore, IC50 could then be determined at the point of intersection with the x-axis [16].

Discussion
Wild medicinal plants present a vast amount of new compounds, which can be used in the modern pharmaceutical research.
Nowadays, up to 60% of the currently used anti-tumorigenic drugs, are derived from natural sources [18][19]. The use of natural alternative medicines becomes urgently and necessary. Previous studies of Rashid et al. [20] were carried to test extracts of L. nudicaulis and L. resedifolia (as quoted by González [21], Launaea fragilis is the correct name for the latter species) against beetles and larvae, also he stated that both attain cytotoxic activities.
Launaea fragilis is common, polymorphic and possesses a wide range of tolerance [22]. It contained some phenolic compounds such as flavonoids, coumarins, saponins and phenolic acids [12,14].
The incubation of L. fragilis with H1299 resulted in a strong inhibition for the growth of cancer cells, while, the moderate effect was recorded for Hep G2, Caco-2 and HCT116. On the other hand, the lowest inhibition value is recorded for PC-3. Launaea fragilis is commonly used in the traditional medicine for the treatment of hepatic pains and gastric disorders as reported by Cheriti et al. [9].
Launaea nudicaulis is considered a polymorphic common species in the Egyptian floras [15,22]. Various extracts from aerial parts of the plant exhibited significant scavenging activity; as a result, it can protect the body from damages caused by free radical induced oxidative stress. This higher antioxidant activity was referred to the presence of natural products such as flavonoids, tannins, cardinolids alkaloids, saponins and terpenes [23][24].
Launaea nudicaulis inhibited efficiently the cell proliferation of H1299. Subsequently, HCT116, Caco-2, Hep G2 and PC-3 cell lines exhibit moderate suppression of the cell proliferation, however, MCF7 revealed the lowest inhibition value. This species was traditionally used to treat gastric burns, stomach pain and constipation. Also, it was useful for hemorrhoids, children fever, in addition to the treatment of skin itches and eczema [9]. Similarly, Khan et al. [25] tested the alcoholic extract of Launaea procumbens and reported its significance in the inhibition of the tumor with IC50= 13±0.2 μg/mL. As well, the methanol extract of Launaea mucronata was evaluated against breast (MCF7), hepatocarcinoma (Hep G2), colon adenocarcinoma (HCT116) and cervix (HeLa) cell lines with IC50= 12.70, 19.60, 19 and 12.60 μg/ml; respectively [26].

Conclusion
Anti-proliferative effect of L. fragilis and L. nudicaulis ethanol extracts can act as bioactive sources of natural anticancer agents.
Ethanol extract of L. nudicaulis is more effective in the inhibition of the cell proliferation than that of L. fragilis, for the six investigated cell lines. This may be ascribed to the higher antioxidant activity of the former species relative to the latter.