1. Introduction
Learning about the plants and seeds that cover a large portion of the earth and seeking remedies for many diseases by including plants in their lives has been a method used by humanity since the beginning of time., the active substances obtained with this method constitute the building blocks of drugs used for current diseases. In contrast to synthetic therapy (chemotherapy, radiotherapy, and other drug agents) beneficial herbs symbolize safety [
1] and play a major role in treatment processes, including cancer treatment [
2,
3,
4,
5]. In additio experimental and clinical Chinese medicine treatment methods demonstrated effectiveness of many herbal formulations in the treatment of cancer at various stages [
6]. Plants are source of biologically active substances, and in epidemiological studies, certain foods, such as vegetables, fruits, and dietary fiber, have been shown to act as chemo-preventive agents[
7]. Additionally, in recent records, it is reported that 80% of people living in rural areas use medicinal plants to solve their basic health problems [
8], and 700 plant species identified in the Middle East region have medicinal value[
9]. The perennial pipe (
Campsis radicans L.) plant is widely distributed in the USA, Canada, China, and South Asia [
10] and is grown as an ornamental plant in parks and roadsides [
11], and used in traditional medicine for the treatment of infections caused by Candida, Haemophilus, etc. [
12].
DPPH scavenging activity, thrombolytic activity, analgesic activity, hypoglycemic activity, antidiarrheal activity, and CNS antidepressant activity of
Campsis radicans L. plant were investigated by creating experimental models. According to the results of this study, it was revealed that C. radicans has significantly high antioxidant, thrombolytic, membrane stabilizing, analgesic hypoglycemic, antidiarrheal, and CNS antidepressant activities [
13]. In our literature review, we could not find a significant study showing the antiapoptotic effects of C. radicans in the human colon adenocarcinoma cell line (HT-29). To compensate for this deficiency, cytotoxic activity experiments were also performed on the HT-29 cell line. is the decision whether the compounds obtained from plants can be used as medicine is made through many clinical studies and computer simulations. In this process, simulations can show the ADMET properties of ligands, drug affinities, and their interactions with the active site of the target protein with almost complete accuracy at a low cost. Knowing these properties is one of the first steps to decide whether the obtained ligand can be used in clinical trials. In our study, using computer simulations and some important databases, the properties of the phenolic compounds of the C. radicans plant, such as drug properties and whether they can bind to the active sites of proteins that play an important role in cancer, were also investigated.
3. Results
The heavy mineral content of the
Campsis radicans plant L. is shown in
Table 1 and elements such as Ag, As, Ba, Cd, Co, Sn, and Tl could not be detected. Evaluations were performed according to the normal and toxic concentrations found in medicinal plants, which were previously studied [
27]. As a result, while Mn, Pb and Zn concentrations in
Campsis radicans L. plant were observed to be within safe limits, while Cr, Cu, Fe, Mo, Ni, and V elements were found to be above the safe limits.
Total phenolic and flavonoid contents in the extracts (
Tables S3 and S4) of
Campsis radicans L. plant prepared with three different solvents are shown in
Figure 1 Significant differences were found between total phenolic and flavonoid amounts in the extracts prepared with water, ethanol, and ether (p<0.0001). % DPPH and % ABTS inhibition capacities in extracts prepared with three different solvents are shown in
Figure 2 Significant differences were found between the three methods and the %DDPH and %ABTS inhibition capacities (p<0.0001).
Common names, carbon numbers, and PubChem CID numbers of fatty acids obtained from GC-MS fatty acid and phenolic content analysis of
Campsis radicans L. plant are shown in
Table 2.
Campsis radicans L. plant extracts (except Ether) were found to have a cytotoxic effect on the HT-29 cell line. The cytotoxic activity increased depending on the dose and the IC50 values of ethanol, water, and ether extracts were found to be, 9.8 mg/mL, 8.47 mg/mL, and 5.8 mg/mL, respectively (
Figure S1).
While
Campsis radicans L. is mentioned as an anticarcinogenic plant in Chinese medicine [
28], there is no study in the literature to support this idea. In order to close this gap, we performed cytotoxic activity experiments on the HT-29 cell line and found that the aqueous extract of the plant showed increased cytotoxic activity in a dose-dependent manner. This completes the information on the cytotoxic activity of
Campsis radicans L. and acts as the first step to closing a major gap in the literature. Plants can demonstrate their anticarcinogenic and antimicrobial activities with their phenolic and flavonoid contents. Phenolic and flavonoid content plays an important role in determining the antioxidant capacity of a plant. There is little so little data in the literature about the antioxidant capacity, as well as phenolic and flavonoid content of the
Campsis radicans L. plant. In the extraction study performed with different solvents, the phenolic capacity of the
Campsis radicans L. plant was found to be between 6.38 and 60.13 mg/GAE [
13]. In our study, the total phenolic content was found to be 0.42 – 2.07 mg/L extract, and the total flavonoid content was found to be 83.4-300.6 mg/L of extract. In addition, the
Campsis radicans L. plant can be a source of antioxidant supplement according to its %DPPH and %ABTS scavenging activities. Heavy metal content analysis of
Campsis radicans L. plant was a missing data in the literature soin order to close this gap with our study, heavy metal content analysis of the plant was performed by ICP-MS. When the region where
Campsis radicans L. is collected is evaluated in terms of air and soil quality, we think that this plant is a plant that can accumulate some minerals. While As, Cd, Co, and Ti metals were not found in the plant, Fe, Cu, Ni, Cr, Mo, and V metals were found above normal concentrations and even at toxic levels for plants. Since the heavy metal content at this high concentration is above medicinal plant standards, we think that the Campsis radicans L. plant should be grown specifically for medicinal purposes.
Molecular interactions of phenolic compounds obtained by GC-MS method with target proteins; the binding energy, the number of hydrogen bonds, and bonded amino acids are shown in
Table 3.
The interactions developed by ligands in the protein active site are conventional hydrogen bonds, carbon-hydrogen bonds, halogen bonds, van der Waals interactions, pi-sigma, pi-alkyl, and alkyl interactions. According to the results obtained in the bonding study, all ligands interacted with the active site of the proteins by making bonds in the appropriate conformation. According to these results, 4-Vinylbenzoic acid, which is one of the phenolics obtained from the aqueous extracts of the plant, has higher binding energy (-5.2 kcal/mol) and 1 conventional hydrogen bond compared to the other aqueous extract ligands, demonstrate distinct interactions with 6 amino acids while binding to the Bax protein active site. Propanoic acid, 2-hydroxy-, 1-methylethyl ester, (2S)-, which bonded with the lowest binding energy (-3.3 kcal/mol) did not form conventional hydrogen bonds but developed different favorable interactions with 4 different amino acids. Trimethyl citrate, which makes 5 conventional hydrogen bonds, is bound to the protein active site with a binding energy of -3.8 kcal/mol. 4-Methoxyphenethyl alcohol, which binds to the active site of the Bcl-2 protein with the highest binding energy, did not make any conventional hydrogen bonds but bonded to the protein’s active site by developing different interactions with 5 different amino acids. 4-Methyl-3,6,9-trioxadecan-1-ol was bound to the protein active site with the lowest binding energy (-3.2 kcal/mol) and made 1 conventional hydrogen bond. Trimethyl citrate, which binds to the protein active site with the most conventional hydrogen bond, made 5 conventional hydrogen bonds. The binding energy to the protein active site was -4.2 kcal/mol. Levoglucosan, which binds to the Caspase-3 protein active site with the highest binding energy (-4.9 kcal/mol), was bound to the protein active site by conventional hydrogen bonds and van der Waals interactions. Propanoic acid, 2-hydroxy-, 1-methylethyl ester, (2S)- bonded with the lowest binding energy (-3.7 kcal/mol) to the protein active site by developing appropriate interactions with 4 different amino acids that have made 2 conventional hydrogen bonds. Trimethyl citrate, which made ten conventional hydrogen bonds, was bound to the protein active site with a binding energy of -4.3 kcal/mol. 6-nitro-3-phenyl-1H-indol-2-amine, which is one of the phenolics obtained from the ethanolic extracts of the plant, develops a conventional hydrogen bond with the highest binding energy (-5.8 kcal/mol) to the Bax protein active site and performed different interactions with 4 different amino acids. While vitamin E, which binds with the lowest binding energy (-4.4 kcal/mol), does not develop any conventional hydrogen bonds, it binds to the active site of Bax protein by developing different interactions with 4 different amino acids. 2-methyl-2,3-dihydro-1H-inden-1-ol, which interacted with most amino acids, did not develop conventional hydrogen bonds and was bound to the active site of the Bax protein with a binding energy of -5.3 kcal/mol. The 6-nitro-3-phenyl-1H-indole-2-amine Bcl-2 protein binds to its active site with the highest binding energy (-6.9 kcal/mol) and also has different interactions with 1 amino acid and made 1 conventional hydrogen bond. Vitamin E, which binds with the lowest binding energy, binds to the active site of the Bcl-2 protein by performing different interactions with 5 different amino acids and made 1 conventional hydrogen bond.
The caspase-3 protein binds to the active site of the protein by performing 2 conventional hydrogen bonds and different interactions with 2 different amino acids to 6-nitro-3-phenyl-1H-indole-2-amine, which binds to the active site with the highest binding energy (-6.8 kcal/mol). 2-methyl-2,3-dihydro-1H-inden-1-ol, which binds to Caspase-3 protein with the lowest binding energy (-4.8 kcal/mol), did not develop any conventional hydrogen bonds while bonded to the protein active site by developing different interactions with 3 different amino acids.
The relationships of the phenolic compounds obtained from
Campsis radicans L plant extracts by GC-MS method with the active sites of three proteins (Bax, Bcl-2, and Caspase-3) that play an important role in the apoptotic pathway was observed by using the molecular coupling method; additionally, the drug properties of these phenolic compounds were also analyzed by using databases. In the literature, there is information about the production of
Campsis radicans L. plant phenolics, but the lack of in-silico studies on these phenolic compounds creates a big gap in the literature. To close this gap, our study tested the ADMET properties of phenolic compounds and their compliance with the Lipinski, Veber, and Ghose rules, which are the rules for drug specifications. According to the Lipinski rules, in order to be considered as a drug, a ligand must have some specifications: molecular weight <500g/mol, Log P ≤ 5, hydrogen bond donor ≤5, hydrogen bond acceptor ≤10, and molar break value between 4-130 [
29]. According to Veber’s rules, required specifications for a ligand to be considered as a drug; hydrogen bonding ≤12, rotatable bonds ≤10, polar surface area ≤140, and oral bioavailability >20% [
30]. According to Ghose’s rules, the properties that the drug candidate ligand should have are LogP -0.4 - 5.6, molar refraction 40 - 150, molecular weight 160 - 480 g/mol, the atomic number between 20 and 70, and polar surface area <140 [
31].
The findings of our study show that the
Campsis radicans L. plant can be used as an antioxidant source due to its phenolic and flavonoid capacity, and this antioxidant feature also contributes to anticarcinogenic activity. Compliance of phenolic compounds with drug rules and ADMET properties (
Tables S5 and S6) was also investigated. It was shown that the obtained phenolic compounds were bonded to the active sites of proteins by in-silico studies. However, bonding and other in-silico studies are the results of predictions made within algorithms. For this reason, more clinical studies on these phenolic compounds are required.