A series of usnic acid benzylidene derivatives (groups I-V) were designed, synthesized and evaluated for their anticancer activity in the search for potentially new anticancer agents. Compounds 1a, 5b, 2b, 2e and 2f exhibited the most potent cytotoxcity against K562 cell line with IC 50 values of 10.

A series of lupeol derivatives 2, 2a-2f, 2a-2h, 3a-3e, and 4a-4b were designed, synthesized and evaluated for their α-glucosidase inhibitory and cytotoxic activities. Among synthetic derivatives, lupeol analogues 2b and 2e containing a benzylidene chain exhibited the best activity against α-glucosidase and superior to the positive agent with the IC 50 values of 29.4 ± 1.33 and 20.1 ± 0.91 μM, respectively. Lupeol analogues 2d and 3a showed weak cytotoxicity against K562 cell line with the IC 50 values of 76.6 ± 2.40 and 94.4 ± 1.51 μM, respectively.

Lichen-derived depsidones have been a successful source for alpha-glucosidase inhibitory agents with numerous advantages. In this paper, derivatives of protocetraric acids were designed and synthesized. Diels-Alder reaction, esterification, and Friedel-Crafts alkylation of protocetraric acid with different reagents under Lewis acid were performed. Eleven products were prepared, including 10 new compounds and parmosidone A. Among them, compounds 2-4 and 6 had the novel skeletons. The newly synthetic products were evaluated for alphaglucosidase inhibition. Among tested compounds, 9 showed the strongest activity, with an IC50 value of 5.9 µM. Molecular docking model indicated the consistency between in vitro and in silico data of alpha-glucosidase inhibition..

This study investigated a set of new potential antidiabetes agents. Derivatives of usnic acid were designed and synthesized. These analogs and nineteen benzylidene analogs from a previous study were evaluated for enzyme inhibition of α‐glucosidase. Analogs synthesized using the Dakin oxidative method displayed stronger activity than the pristine usnic acid (IC50>200 μM). Methyl (2E,3R)‐7‐acetyl‐4,6‐dihydroxy‐2‐(2‐methoxy‐2‐oxoethylidene)‐3,5‐dimethyl‐2,3‐dihydro‐1‐benzofuran‐3‐carboxylate (6b) and 1,1′‐(2,4,6‐trihydroxy‐5‐methyl‐1,3‐phenylene)di(ethan‐1‐one) (6e) were more potent than an acarbose positive control (IC50 93.6±0.49 μM), with IC50 values of 42.6±1.30 and 90.8±0.32 μM, respectively. Most of the compounds synthesized from the benzylidene series displayed promising activity. (9bR)‐2,6‐Bis[(2E)‐3‐(2‐chlorophenyl)prop‐2‐enoyl]‐3,7,9‐trihydroxy‐8,9b‐dimethyldibenzo[b,d]furan‐1(9bH)‐one (1c), (9bR)‐3,7,9‐trihydroxy‐8,9b‐dimethyl‐2,6‐bis[(2E)‐3‐phenylprop‐2‐enoyl]dibenzo[b,d]furan‐1(9bH)‐one (1g), (9bR)‐2‐acetyl‐6‐[(2E)‐3‐(2‐chlorophenyl)prop‐2‐enoyl]‐3,7,9‐trihydroxy‐8,9b‐dimethyldibenzo[b,d]furan‐1(9bH)‐one (2d), (9bR)‐2‐acetyl‐6‐[(2E)‐3‐(3‐chlorophenyl)prop‐2‐enoyl]‐3,7,9‐trihydroxy‐8,9b‐dimethyldibenzo[b,d]furan‐1(9bH)‐one (2e), (6bR)‐8‐acetyl‐3‐(4‐chlorophenyl)‐6,9‐dihydroxy‐5,6b‐dimethyl‐2,3‐dihydro‐1H‐[1]benzofuro[2,3‐f][1]benzopyran‐1,7(6bH)‐dione (3e), (6bR)‐8‐acetyl‐6,9‐dihydroxy‐5,6b‐dimethyl‐3‐phenyl‐2,3‐dihydro‐1H‐[1]benzofuro[2,3‐f][1]benzopyran‐1,7(6bH)‐dione (3h), (6bR)‐3‐(2‐chlorophenyl)‐8‐[(2E)‐3‐(2‐chlorophenyl)prop‐2‐enoyl]‐6,9‐dihydroxy‐5,6b‐dimethyl‐2,3‐dihydro‐1H‐[1]benzofuro[2,3‐f][1]benzopyran‐1,7(6bH)‐dione (4b), and (9bR)‐6‐acetyl‐3,7,9‐trihydroxy‐8,9b‐dimethyl‐2‐[(2E)‐3‐phenylprop‐2‐enoyl]dibenzo[b,d]furan‐1(9bH)‐one (5c) were the most potent α‐glucosidase enzyme inhibitors, with IC50 values of 7.0±0.24, 15.5±0.49, 7.5±0.92, 10.9±0.56, 1.5±0.62, 15.3±0.54, 19.0±1.00, and 12.3±0.53 μM, respectively.

Twelve benzylidene derivatives, one Baeyer-Villiger oxidative, six imine derivatives were successfully designed and synthesized from phyllanthone. In the search for potential new anti-diabetic agents, phyllanthone along with its benzylidene and oxidation analogues were evaluated for enzyme inhibition against α-glucosidase. In the benzylidene series, most analogues displayed stronger activity than the mother compound. 1c revealed the strongest activity, outperforming the acarbose positive control with an IC 50 value of 19.59 µM. Phyllanthone and its derivatives were then tested for cytotoxic activity against the K562 cell line. The imine analogues displayed the most powerful cytotoxic activity with 3c, 3d having IC 50 values of 57.55 and 68.02 µM, respectively. KeywordsPhyllanthus (Phyllanthaceae); phyllanthone derivatives; α-glucosidase inhibition; cytotoxic activity General procedure for the synthesis of hydrazine reagents N1-N6 Aryloxyaxetohydrazides (N1, m.p. 138-139 o C; N2, m.p. 105-106 o C) were prepared from appropriate phenols using the method in our previous work (Cong et al. 2007). Benzohydrazide (N3, m.p. 130-131 o C) was prepared from 2-phenylacetic acid by esterification and then hydrazination following the method of (Xu et al.2018). In the same manner with N3, 5-chloro-2hydroxybenzohydrazide (N4, 174 o C) was prepared from 5-chloro-2-hydroxybenzoic acid following the method of (Xu et al. 2018). 2-Hydroxy-5-iodobenzohydrazide (N5, m.p. 178 o C) was prepared from salicylic acid according to the method in those published (Al-Omran and El-Khair, 2016).