Cryptolepine, an indoloquinoline alkaloid, in the management of diabetes mellitus and its associated complications

Structural Simplification of Cryptolepine to Obtain Novel Antifungal Quinoline Derivatives against Phytopathogenic Fungi

A series of quinoline derivatives were designed and synthesized by the structural simplification of cryptolepine and evaluated for their fungicidal activity against six phytopathogenic fungi. Most of these compounds exhibited remarkable activities against Botrytis cinereain vitro. Among them, compounds A18 and L01 showed superior antifungal activity. Significantly, compared to cryptolepine, compound A18 exhibited broad-spectrum inhibitory activities against B. cinerea, Sclerotinia sclerotiorum, Rhizoctonia solani, Phytophthora capsica, Magnaporthe oryzae, and Fusarium graminearum with the respective EC₅₀ values of 0.249, 1.569, 3.915, 0.505, 0.246, and 4.999 μg/mL. Compound L01 displayed the best antifungal activity against B. cinerea with an EC₅₀ value of 0.156 μg/mL. Preliminary mechanistic studies showed that compound A18 could inhibit spore germination, affect the permeability of the cell membrane, increase the content of reactive oxygen species, and affect the morphology of hyphae and cells. Moreover, compound A18 showed excellent in vivo protective effect against B. cinerea, which was more potent than pyrimethanil and equitant to cryptolepine. These results evidenced that compound A18 displayed superior fungicidal activities and could be a potential fungicidal candidate against plant fungal diseases.

Unravelling the pharmacological properties of cryptolepine and its derivatives: a mini-review insight

Cryptolepine (1,5-methyl-10H-indolo[3,2-b]quinoline), an indoloquinoline alkaloid, found in the roots of Cryptolepis sanguinolenta (Lindl.) Schltr (family: Periplocaceae), is associated with the suppression of cancer and protozoal infections. Cryptolepine also exhibits anti-bacterial, anti-fungal, anti-hyperglycemic, antidiabetic, anti-inflammatory, anti-hypotensive, antipyretic, and antimuscarinic properties. This review of the latest research data can be exploited to create a basis for the discovery of new cryptolepine-based drugs and their analogues in the near future. PubMed, Scopus, and Google Scholar databases were searched to select and collect data from the existing literature on cryptolepine and their pharmacological properties. Several in vitro studies have demonstrated the potential of cryptolepine A as an anticancer and antimalarial molecule, which is achieved through inhibiting DNA synthesis and topoisomerase II. This review summarizes the recent developments of cryptolepine pharmacological properties and functional mechanisms, providing information for future research on this natural product.

Mineral Fertilization Influences the Growth, Cryptolepine Yield, and Bioefficacy of Cryptolepis sanguinolenta (Lindl.) Schlt

Cryptolepis sanguinolenta (Lindl.) Schlt., the main source of cryptolepine alkaloid, is intensively exploited in the wild to treat malaria and Lyme disease. In this study, the influence of four inorganic fertilizers (supplying N, P, K, or NPK) and four growth periods (3, 6, 9, and 12 months after transplanting) on the herb's root biomass, cryptolepine content and yield, and biological activities were investigated in a pot and field trial. The results showed the application of N (in the form of Urea or NPK) increased root biomass yield, cryptolepine content, and cryptolepine yield compared to unfertilized plants. The 9-month-old plants recorded the maximum cryptolepine content (2.26 mg/100 mg dry root) and cryptolepine yield (304.08 mg/plant), indicating the perfect time to harvest the herb. Plant age at harvest had a more significant influence (50.6-55.7%) on cryptolepine production than fertilizer application (29.2-33.3%). Cryptolepine extracts from 9- to 12-month-old plants had the highest antiplasmodial activity (IC50 = 2.56-4.65 µg/mL) and drug selectivity index (2.15-3.91) against Plasmodium falciparum Dd2. These extracts were also cytotoxic to Jurkat leukaemia cell lines (CC50 < 62.56 µg/mL), indicating the possible use of cryptolepine for cancer management. Growing the herb in the field increased cryptolepine yield 2.5 times compared to growth in a pot, but this did not influence the antiplasmodial activity of the extract. Commercial cultivation of C. sanguinolenta for 9 months combined with N application could be a promising solution to the sustainable use of this threatened medicinal species.

Synthesis of Isocryptolepine-Triazole Adducts and Evaluation of Their Cytotoxic Activity

Eighteen hybrid compounds between 8-bromo-2-fluoro-isocryptolepine (4) and 1,2,3-triazole were synthesized via azide rearrangement-annulation reaction. Compound 4 underwent regioselective N-propargylation and click reaction to form 8-bromo-2-fluoro-isocryptolepine-triazole hybrids 11 which were evaluated for cytotoxic activity. Compound 11 c containing 1-anisyltriazole was the most effective in inhibiting HepG2, HuCCA-1 and A549 cell lines (IC₅₀ values of 1.65-3.07 μM) while compounds 11 a (1-phenyltriazole), 11 j (1-para-CF₃ -benzyltriazole) and 11 l (1-meta-Cl-benzyltriazole) were potent inhibitors of HuCCA-1, HepG2 and A549 cell lines, respectively. Moreover, 11 l showed the lowest cytotoxicity to normal human kidney cell line. Compounds 11 c and 11 l provided improvement of cytotoxic activity over 4. Compounds 4, 11 c and 11 l were selected to investigate their mechanisms of action. The results showed that 4 could induce G2/M cell cycle arrest and was involved in the upregulation of p53 and p21 proteins. However, the mechanisms of growth inhibition by 11 c and 11 l were associated with G0/G1 cell cycle arrest and mediated by induction of oxidative stress.

Research progress of indole compounds with potential antidiabetic activity

New types of antidiabetic agents are continually needed with diabetes becoming the epidemic in the world. Indole alkaloids play an important role in natural products owing to their variable structures and versatile biological activities like anticonvulsant, anti-inflammatory, antidiabetic, antimicrobial, and anticancer activities, which are a promising source of novel antidiabetic drugs discovery. The synthesized indole derivatives possess similar properties to natural indole alkaloids. In the last two decades, more and more indole derivatives have been designed and synthesized for searching their bioactivities. This present review describes comprehensive structures of indole compounds with the potential antidiabetic activity including natural indole alkaloids and the synthetic indole derivatives based on the structure classification, summarizes their approaches isolated from natural sources or by synthetic methods, and discusses the antidiabetic effects and the mechanisms of action. Furthermore, this review also provides briefly synthetic procedures of some important indole derivatives.

Isobolographic analysis of co-administration of two plant-derived antiplasmodial drug candidates, cryptolepine and xylopic acid, in Plasmodium berghei

Background

Increasing resistance to current anti-malarial therapies requires a renewed effort in searching for alternative therapies to combat this challenge, and combination therapy is the preferred approach to address this. The present study confirms the anti-plasmodial effects of two compounds, cryptolepine and xylopic acid and the relationship that exists in their combined administration determined.

Methods

Anti-plasmodial effect of cryptolepine (CYP) (3, 10, 30 mg kg⁻¹) and xylopic acid (XA) (3, 10, 30 mg kg⁻¹) was evaluated in Plasmodium berghei-infected male mice after a 6-day drug treatment. The respective doses which produced 50% chemosuppression (ED₅₀) was determined by iterative fitting of the log-dose responses of both drugs. CYP and XA were then co-administered in a fixed dose combination of their ED₅₀s (1:1) as well as different fractions of these combinations (1/2, 1/4, 1/8, 1/16 and 1/32) to find the experimental ED₅₀ (Z_exp). The nature of interaction between cryptolepine and xylopic acid was determined by constructing an isobologram to compare the Z_exp with the theoretical ED₅₀ (Z_add). Additionally, the effect of cryptolepine/xylopic acid co-administration on vital organs associated with malarial parasiticidal action was assessed.

Results

The Z_add and Z_exp were determined to be 12.75 ± 0.33 and 2.60 ± 0.41, respectively, with an interaction index of 0.2041. The Z_exp was significantly (P < 0.001) below the additive isobole indicating that co-administration of cryptolepine and xylopic acid yielded a synergistic anti-plasmodial effect. This observed synergistic antiplasmodial effect did not have any significant deleterious effect on the kidney, liver and spleen. However, the testis were affected at high doses.

Conclusion

The co-administration of cryptolepine and xylopic acid produces synergistic anti-malarial effect with minimal toxicity.

Phytochemical and Pharmacological Review of Cryptolepis sanguinolenta (Lindl.) Schlechter

Ethnopharmacological Relevance

Cryptolepis sanguinolenta is a scrambling thin-stemmed shrub found in Africa. Traditionally in West Africa, it is employed in the treatment of malaria, diarrhea, and respiratory conditions. This review discusses the traditional importance as well as the phytochemical, ethnomedical, pharmacological, and toxicological importance of this plant.

Materials and Methods

Excerpta Medica Database, Google Scholar, Springer, and PubMed Central were the electronic databases used to search for and filter primary studies on Cryptolepis sanguinolenta.

Results

The detailed review of various studies conducted on C. sanguinolenta and some of its constituents gives an important body of proof of its potential therapeutic benefits and also of its use as a source of lead compounds with therapeutic potentials.

Conclusion

The review on C. sanguinolenta is important in identifying grey areas in the research on this medicinal plant and also provides comprehensive data thus far to continue research on this plant.