Abstract
Marine compound dendrodoine was first obtained from tunicate species ( Dendrodo grossularia ). It has a five-membered ring, namely, it is a heterocycle thiadiazole, which is found rarely in natural sources . Following its biological activities, novel analogs have been investigated recently. Synthesis of the analogs for this study is realized with uncommon thiazole closure, including methylene-carbonyl condensation. Structures are elucidated by NMR ( 1 , 13 C) and HRMS spectrums. As an alkaloid derivative, antioxidant properties were evaluated with DPPH and FRAP assays and antimicrobial effect with microdilution method. Among the series, 3bc-3cf showed higher antioxidant activity than those having 3 or 4-pyridyl substituents. There is lesser activity for 2-pyridyl activity for 2-pyridyl containing group, which may be a result of intramolecular interactions. No activity was observed against gram-negative bacteria at 250 μg/mL. 3ae and 3ce showed activity at 64 μg/mL against S. aureus and 3ae showed activity at 16 μg/mL against S. epidermidis gram-positive bacteria. Chloramphenicol showed activity against all microorganisms at 8–16 μg/mL. Sixteen original dendrodoine analogs have been defined by close/higher activity compared to dendrodoine analogs and Trolox.
Highlights
Marine tunicates are animals living in different deepness levels of oceans and are usually attached to docks
After 15 min stirring, 250 mmol bromine was added quite slowly to the mixture. It was checked with thin-layer chromatography that reaction ended, and solid material was gathered on the bottom
Ten-microliter compounds of different concentrations (0.312 μM, 0.625 μM, 1.25 μM, 2.5 μM, 3.75 μM, 5 μM) dissolved in DMSO below 1% were mixed with 230 uL of FRAP reagent and 10 uL dH2O in a 96-well microtiter plate
Summary
Marine tunicates are animals living in different deepness levels of oceans and are usually attached to docks. Dendrodoine is an alkaloid that was isolated from Dendroda grossular indigenous in North Britain in 1980 [1]. Dendrodoine synthesis was accomplished 4 years after the first isolation. It has a thiadiazole ring which is rarely found in natural compounds, and it is known to be a part of functional synthetic compounds [2]. Beyond its unique thiadiazole ring, it is a bioisoster of aminothiazoles. Aminothiazoles have a diverse biological spectrum including anticancer, antimicrobial, antioxidant, antidiabetic, anticonvulsant, antiinflammatory, antihypertensive, and protective activities. There are approved drugs, such as meloxicam, cefdinir, famotidine, bearing this moiety [3,4,5]
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