Antifungal Quinoline Alkaloids from Waltheria indica

Abstract

Chemical investigation of a dichloromethane extract of the aerial parts of Waltheria indica led to the isolation and characterization of five polyhydroxymethoxyflavonoids, namely, oxyanin A (1), vitexicarpin (3), chrysosplenol E (4), flindulatin (5), 5-hydroxy-3,7,4'-trimethoxyflavone (6), and six quinolone alkaloids, waltheriones M-Q (2, 7, 8, 10, 11) and 5(R)-vanessine (9). Among these, compounds 2, 7, 8, 10, and 11 have not yet been described in the literature. Their chemical structures were established by means of spectroscopic data interpretation including (1)H and (13)C, HSQC, HMBC, COSY, and NOESY NMR experiments and UV, IR, and HRESIMS. The absolute configurations of the compounds were established by ECD. The isolated constituents and 10 additional quinoline alkaloids previously isolated from the roots of the plant were evaluated for their in vitro antifungal activity against the human fungal pathogen Candida albicans, and 10 compounds (7, 9, 11-16, 18, 21) showed growth inhibitory activity on both planktonic cells and biofilms (MIC ≤ 32 μg/mL). Their spectrum of activity against other pathogenic Candida species and their cytotoxicity against human HeLa cells were also determined. In addition, the cytological effect of the antifungal isolated compounds on the ultrastructure of C. albicans was evaluated by transmission electron microscopy.

Identification and Mode of Action of a Plant Natural Product Targeting Human Fungal Pathogens

“…Most of the compounds (25 out of 33) were active against biofilms and exhibited a MIC against biofilm cells higher than the MICs measured against planktonic cells, except for NPs originating from Waltheria indica . The antibiofilm activity of these NPs was previously reported ( 15 ).…”

Quinolone derivatives and their antifungal activities: An overview

“…Various 4‐quinolone natural products and their derivatives have been screened for their in vitro antifungal activities, but most of them are far less active than the references . In spite of that, the enriched SAR may pave the way for the further rational development of 4‐quinolone derivatives with excellent potency against both drug‐susceptible and drug‐resistant fungi.…”

Synthesis and Biological Activity of 2-Arylidene-N-(quinolin-6-yl)hydrazine-1-carboxamides

“…Despite a number of active agents available today, it is still a huge clinical demand to discover more effective agents [5]. Quinoline ring system is the pharmacologically important structural scaffold displaying a wide range of biological activities [6][7][8][9][10]. Neratinib (Figure 1) is a quinoline derivative which was approved by FDA for the treatment of HER-2 breast cancer in patients [11].…”