Melanoma is among the most aggressive and treatment-resistant cancers. Currently, available therapies for melanoma are not satisfactory, and the prognosis for patients with metastatic melanoma is still poor. Vemurafenib, a BRAF kinase inhibitor (BRAFi), provides an approximately 50% response rate in patients with metastatic melanoma, but eventually, relapse occurs due to acquired resistance to the drug. Novel therapeutics and BRAFi adjuvants for treating melanoma are needed. Si-Jun-Zi-Tang (SJZT) is a traditional Chinese medicine formula used to treat chronic and debilitating diseases including melanoma. SJZT-based therapies alone or in combination with chemotherapies have achieved good clinical outcomes in melanoma management. However, the pharmacological basis of SJZT for its clinical use in melanoma treatment is not fully understood. c-Met is a receptor tyrosine kinase (RTK), and hepatocyte growth factor (HGF) is the only known ligand of c-Met. Abnormal activation of HGF/c-Met has been implicated in melanoma progression. HGF/c-Met has been proposed as a therapeutic target for melanoma. Some bioactive constituents in SJZT have been shown to inhibit c-Met signaling. In this study, we investigated the anti-melanoma effects and c-Met signaling-related action mechanisms of SJZT. Our in vivo study showed that SJZT-A, an ethanolic extract of SJZT, inhibited B16 tumor growth in mice without overt toxicity. Mechanistic investigations revealed that SJZT-A elevated miR-34b (a tumor-suppressing miRNA), and lowered c-Met (a miR-34b target gene) and β-catenin (a downstream molecule of c-Met signaling) expression levels in the B16 tumors. But SJZT-A failed to reduce the viability of B16 and A375 melanoma cells. Active component-enriched SJZT-B, which was prepared from SJZT-A using macroporous resin column chromatography, exhibited potent anti-proliferation effect and inhibited miR-34b/c-Met/β-catenin signaling in cultured melanoma cells. Overexpression of constitutively active β-catenin partially diminished the inhibitory effect of SJZT-B on cell proliferation. SJZT-B also exerted anti-proliferative effects, inhibited c-met signaling, and induced ER stress in vemurafenib resistance melanoma cells. In vivo experiments showed that intragastric administration of SJZT-B for consecutive 14 days overcame vemurafenib resistance in melanoma-bearing mice without observable toxicities. Overall, these results indicate that SJZT has anti-melanoma effects and is relatively safe. Also, we found that licochalcone A, a flavonoid presented in SJZT-B, overcame vemurafenib resistance both in vitro and in vivo, as well as inhibited c-Met signaling and induced ER stress in A375-VR cells, which is in line with the effects of SJZT-B in melanoma. The role of triggering ER stress in licochalcone A's effects in overcoming vemurafenib resistance effects has also been established. Overall, these results suggest that licochalcone A is one of the active compounds responsible for the anti-melanoma effects of SJZT-B. In conclusion, our results demonstrated that SJZT has anti-melanoma effects and is safe in cell and mouse melanoma models. Licochalcone A has been identified to be one of the active components responsible for the anti-melanoma effects of SJZT. This study provides a pharmacological and chemical basis for the traditional use of the formula SJZT in treating melanoma, and suggests that SJZT and SJZT-derived compounds have the potential to be developed as modern alternative and/or complementary agents for melanoma management.

Melanoma is among the most aggressive and treatment-resistant cancers. Currently, available therapies for melanoma are not satisfactory, and the prognosis for patients with metastatic melanoma is still poor. Vemurafenib, a BRAF kinase inhibitor (BRAFi), provides an approximately 50% response rate in patients with metastatic melanoma, but eventually, relapse occurs due to acquired resistance to the drug. Novel therapeutics and BRAFi adjuvants for treating melanoma are needed. Si-Jun-Zi-Tang (SJZT) is a traditional Chinese medicine formula used to treat chronic and debilitating diseases including melanoma. SJZT-based therapies alone or in combination with chemotherapies have achieved good clinical outcomes in melanoma management. However, the pharmacological basis of SJZT for its clinical use in melanoma treatment is not fully understood. c-Met is a receptor tyrosine kinase (RTK), and hepatocyte growth factor (HGF) is the only known ligand of c-Met. Abnormal activation of HGF/c-Met has been implicated in melanoma progression. HGF/c-Met has been proposed as a therapeutic target for melanoma. Some bioactive constituents in SJZT have been shown to inhibit c-Met signaling. In this study, we investigated the anti-melanoma effects and c-Met signaling-related action mechanisms of SJZT. Our in vivo study showed that SJZT-A, an ethanolic extract of SJZT, inhibited B16 tumor growth in mice without overt toxicity. Mechanistic investigations revealed that SJZT-A elevated miR-34b (a tumor-suppressing miRNA), and lowered c-Met (a miR-34b target gene) and β-catenin (a downstream molecule of c-Met signaling) expression levels in the B16 tumors. But SJZT-A failed to reduce the viability of B16 and A375 melanoma cells. Active component-enriched SJZT-B, which was prepared from SJZT-A using macroporous resin column chromatography, exhibited potent anti-proliferation effect and inhibited miR-34b/c-Met/β-catenin signaling in cultured melanoma cells. Overexpression of constitutively active β-catenin partially diminished the inhibitory effect of SJZT-B on cell proliferation. SJZT-B also exerted anti-proliferative effects, inhibited c-met signaling, and induced ER stress in vemurafenib resistance melanoma cells. In vivo experiments showed that intragastric administration of SJZT-B for consecutive 14 days overcame vemurafenib resistance in melanoma-bearing mice without observable toxicities. Overall, these results indicate that SJZT has anti-melanoma effects and is relatively safe. Also, we found that licochalcone A, a flavonoid presented in SJZT-B, overcame vemurafenib resistance both in vitro and in vivo, as well as inhibited c-Met signaling and induced ER stress in A375-VR cells, which is in line with the effects of SJZT-B in melanoma. The role of triggering ER stress in licochalcone A's effects in overcoming vemurafenib resistance effects has also been established. Overall, these results suggest that licochalcone A is one of the active compounds responsible for the anti-melanoma effects of SJZT-B. In conclusion, our results demonstrated that SJZT has anti-melanoma effects and is safe in cell and mouse melanoma models. Licochalcone A has been identified to be one of the active components responsible for the anti-melanoma effects of SJZT. This study provides a pharmacological and chemical basis for the traditional use of the formula SJZT in treating melanoma, and suggests that SJZT and SJZT-derived compounds have the potential to be developed as modern alternative and/or complementary agents for melanoma management.

Background: Natural products have attracted high attention due to their great contribution in drug discovery. Many natural products have shown to be effectively against different disease targets including cancer, malaria and HIV. And their structural diversity is a rich resource for the discovery of novel bioactive compounds. This thesis is to explore plant natural products for their potential in treatment of malaria and cancer diseases. Malaria is still considered as a major global health problem, affecting a large population of the world, especially in the developing countries. Effective drug discovery is still one of the main efforts to control malaria, and plant-derived compounds have played the most important role for treatment of malarial disease. In our previous work, we have evaluated more than 2,000 plant extracts against the malaria parasite Plasmodium falciparum. As a result, we discovered dozens of antiplasmodium plant leads. Bioassay guided separation of these active plant extracts led to isolation of some potent antimalarial compounds. Among them, trichothecenes, the sesquiterpenes identified from the plant Ficus fistulosa and Rhaphidophora decursiva, were found to have potent inhibitory activity against P. falciparum with IC50 values in the sub-nano molar range in our previous study (Zhang et al. 2002). However, these compounds are significant cytotoxic. In order to improve the antimalarial activity of the trichothecenes, we evaluated the antimalarial activity of dozens of trichothecenes, and based on the structure-activity relationships (SAR) analysis, we synthesized trichothecene derivatives with low cytotoxicity. On the other hand, cancer has stricken one-third of the world's population. Through our anticancer drug program to discover bioactive leads from thousands of the plant extracts, the extract of Miliusa sinensis Finet et Gagnep. (Annonaceae) was found to exhibit cytotoxic activity against a panel of cancer cell lines. Our previous bioassay-directed fractionation of the leaf, twig and flower extracts of M. sinensis has led to the discovery of a novel class of anticancer lead molecules, which we designated as miliusanes (Zhang et al, 2006). M. balansae, in the same family with M. sinensis, also contains bioactive miliusanes. We thus collected the plant materials of M. balansae to isolated additional new anticancer miliusanes. Objective: The objective of this study is to discover novel antimalarial and anticancer natural compounds from plants using different techniques in combination of extensive literature review, phytochemical separation, SAR analysis, semi-synthesis and biological activity study. Trichothecenes and miliusanes are the two major classes of the compounds, which have been extensively explored in the current thesis for their antimalarial and anticancer potential.;Methodology: There was a prior comprehensive review article entitled "Antimalarial activity of plant metabolites" by Schwikkard and Van Heerden (2002), which reported structures of those antiplasmodial active compounds and covered literatures up to the year 2000. As a continuation of their work, antimalarial compounds isolated from plants, including marine plants, which reported in the literatures from 2001 to the end of 2017 have been reviewed and organized according to their plant families. Dozens of trichothecenes have been obtained by us and explored for their SARs. Based on the SAR analysis, we designed and carried out the structure modifications of some trichothecenes. These compounds were evaluated for their antimalarial and cytotoxic activities. M. balansae, in the same genus with M. sinensis, was selected to isolate bioactive miliusanes, as well as the other active components through bioassay-guided fractionation study. Columns chromatography was used in fractionation and separation of the dichloromethane extract of M. balansae. Preparative HPLC separation and LC-MS analysis were used to speed up the isolation process. All isolates were determined for their chemical structures by spectroscopic means such as NMR and MS, and then evaluated for their anticancer potential. The isolated compounds with abundant amounts were further explored to modify their structures in order to improve their biological activities. Result: During the span of the last 17 years (2001-2017), 175 antiplasmodial compounds were discovered from plants. These active compounds were organized in our review article according to their plant families. In addition, we also included ethnobotanical information of the antimalarial plants. In order to decrease toxicity while retaining antimalarial activity of the trichothecenes, we analyzed SAR of 28 trichothecene analogues. Based on the SAR analysis, we were able to conclude that the diacetylation of C-4 and C-15, and the hydroxylation at C-3 or C-4 could significantly improve the therapeutic indices of trichothecenes. Subsequently, our synthesis of a trichothecene derivative demonstrated potent inhibitory activity against P. falciparum with an IC50 value of 10.4 nM and low toxicity against KB cells with an IC50 value of 556 nM. The separation of the dichloromethane extract of M. balansae led to the isolation of 16 new miliusanes, along with 12 known ones, and 6 flavonoids. Seven of them exhibited significant cytotoxicity against human colorectal cancer cell lines HCT116 with IC50 values in the range of 1.24 - 4.2 µM. The SAR study of the miliusanes indicated that the α,β-unsaturated ketone was the active group of but may not be the essential group responsible for the bioactivity of miliusanes. Two flavonoids that showed moderate cytotoxic activity were carried out their structure activities modification. A total of 19 derivatives have been synthesized based on the two flavonoid structures.

The water solubility of drug molecules plays an important role in consideration of formulation development to treat a wide range of diseases. In this project, two kinds of drug delivery systems, cyclodextrins and liposomes, were developed for insoluble drug delivery to treat Alzheimer's disease (AD) and colorectal cancer (CRC), respectively. AD is an irreversible neurodegenerative disorder associated with the accumulation of amyloid-beta (A??) fibrils. Approximately 10% of people aged 65 and above have AD. Crocetin (CRT) is an active compound isolated from the fruits of gardenia (Gardenia jasminoides Ellis) and the stigmas of saffron (Crocus sativus L.). It has been reported to show various neuroprotective activities. However, poor water solubility and bioavailability are the major obstacles in developing pharmaceutical formulations of CRT. To address the issues, CRT liposomal formulations and CRT-cyclodextrin inclusion complexes were developed and evaluated. CRT-cyclodextrin inclusion complexes significantly increased the water solubility of CRT from the range ??g/mL to mg/mL. The CRT-??-cyclodextrin inclusion complex (1:3 molar ratio of CRT/??-cyclodextrin) was chosen for further studies as it showed the highest encapsulation efficiency (94.73 ?? 0.86%). The formulation had no toxicity to neuronal cells nor AD model cells within the experimental concentration range (0.625 to 100 ??M of CRT). It could downregulate the expression of C-terminus fragments and decrease both intracellular and extracellular levels of A??, which are hallmarks of AD. It also showed dose-dependent neuroprotective and antioxidant effects against H2O2-induced cell death. Pharmacokinetics and biodistribution studies showed that this CRT-??-cyclodextrin inclusion complex was suitable for intravenous administration. The formulation significantly increased the bioavailability of CRT and facilitated CRT crossing the blood-brain barrier to enter the brain. Similar to AD, CRC is increasingly prevalent with aging populations. Approximately 60% of CRC patients are aged 70 and above. Halofuginone (HF) is an active pharmaceutical ingredient (API) originated from Chinese quinine (Dichroa febrifuga Lour.) and artesunate (ART) is a semi-synthetic derivative of artemisinin (ATS) extracted from annual wormwood (Artemisia annua L.). Both APIs show anticancer activities by inhibiting the growth of CRC. However, low aqueous stability limits their applications. Liposome formulation with surface functionalization by CPP2 cell-penetrating peptide was developed to deliver HF and ART for targeted CRC therapy. CPP2 is a peptide that can selectively penetrate colon cancer cells. The liposomal drug formulations had uniform particle size (about 100 nm), high encapsulation efficiency (over 80%) and good stability upon 14 days of storage. In cellular uptake study, CPP2-modified liposome showed stronger permeability and selectivity to colon cancer lines without inducing lysosomal degradation. CPP2 surface-modified liposomal drugs demonstrated greater anticancer activities than free form of drugs or conventional liposomal drugs. Combinations of HF and ART formulations notably decreased cancer cell viability as compared to single formulation alone, which indicated that HF and ART formulations exhibited synergistic anticancer effects at specific ratios. To conclude, the drug delivery systems, cyclodextrins and peptide-modified liposomes, which were developed for AD and CRC treatment, successfully improved the aqueous solubility of insoluble APIs extracted from Chinese medicinal plants.