The synthesis and antistaphylococcal activity of dehydroabietic acid derivatives: Modifications at C-12

Bi- and tricyclic diterpenoids: landmarks from a decade (2013-2023) in search of leads against infectious diseases

Covering: 2013 to 2023In an era where antimicrobial resistance severely threatens our ability to treat infections, the discovery of new drugs that belong to different chemical classes and/or bear original modes of action is urgently needed. In this case, diterpenoids comprise a productive field with a proven track record in providing new anti-infectives to tackle bacterial infections and malaria. This review highlights the potential of both naturally occurring and semi-synthetic bi- and tricyclic diterpenoids to become leads in search of new drugs to treat infections caused by bacteria, fungi, viruses and protozoan parasites. The literature from the last decade (2013-2023) is covered, focusing on naturally occurring and semi-synthetic bicyclic (labdanes and labdane-type) and tricyclic (all classes) diterpenoids, detailing their relevant biological activities in the context of infection, which are explained through structure-activity relationships.

Probing the Interactions of Thiazole Abietane Inhibitors with the Human Serine Hydrolases ABHD16A and ABHD12

12-Thiazole abietanes are highly selective reversible inhibitors of hABHD16A that could potentially alleviate neuroinflammation. In this study, we used synthetic chemistry, competitive activity-based protein profiling, and computational methodologies to try to establish relevant structural determinants of activity and selectivity of this class of compounds for inhibiting ABHD16A over ABHD12. Five compounds significantly inhibited hABHD16A but also very efficiently discriminated between inhibition of hABHD16A and hABHD12, with compound 35 being the most effective, at 100 μM (55.1 ± 8.7%; p < 0.0001). However, an outstanding switch in the selectivity toward ABHD12 was observed in the presence of a ring A ester, if the C2' position of the thiazole ring possessed a 1-hydroxyethyl group, as in compound 28. Although our data were inconclusive as to whether the observed enzyme inhibition is allosteric or not, we anticipate that the structure-activity relationships presented herein will inspire future drug discovery efforts in this field.

Recent Advances on Biological Activities and Structural Modifications of Dehydroabietic Acid

Dehydroabietic acid is a tricyclic diterpenoid resin acid isolated from rosin. Dehydroabietic acid and its derivatives showed lots of medical and agricultural bioactivities, such as anticancer, antibacterial, antiviral, antiulcer, insecticidal, and herbicidal activities. This review summarized the research advances on the structural modification and total synthesis of dehydroabietic acid and its derivatives from 2015 to 2021, and analyzed the biotransformation and structure-activity relationships in order to provide a reference for the development and utilization of dehydroabietic acid and its derivatives as drugs and pesticides.

Synthesis and structure-activity relationships of novel abietane diterpenoids with activity against Staphylococcus aureus

Aim: To find alternative compounds against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA), novel derivatives from dehydroabietic acid were synthesized. Methods & results: Compound 12 was the most effective against 15 MRSA and 11 MSSA with minimum inhibitory concentration values ranging from 3.9 to 15.6 μg/ml. Although less active than 12, compound 11, followed by 25 and 13, also exhibited anti-staphylococcal activity. Additional studies showed that compound 12 is devoid of toxic effect on non-target cells. A structure-activity relationship study revealed that an oxime at C-13 together with a hydroxyl at C-12 could play a key role in the activity. Conclusion: These structures, in particular compound 12, could arise as templates for the development of agents against MRSA and MSSA.

Synthesis and Antiproliferative Evaluation of Novel Hybrids of Dehydroabietic Acid Bearing 1,2,3-Triazole Moiety

To discover novel potent cytotoxic diterpenoids, a series of hybrids of dehydroabietic acid containing 1,2,3-triazole moiety were designed and synthesized. The target compounds were characterized by means of FT-IR, ¹H NMR, ¹³C NMR, ESI-MS and elemental analysis techniques. The in vitro cytotoxicity of these compounds was evaluated by standard MTT (methyl thiazolytetrazolium) assay against CNE-2 (nasopharynx), HepG2 (liver), HeLa (epithelial cervical), BEL-7402 (liver) human carcinoma cell lines and human normal liver cell (HL-7702). The screening results revealed that most of the hybrids showed significantly improved cytotoxicity over parent compound DHAA. Among them, [1-(3-fluorobenzyl)-1H-1,2,3-triazole-4-yl]dehydroabietic acid methyl ester (3c), and [1-(2-nitrobenzyl)-1H-1,2,3-triazole-4-yl]dehydroabietic acid methyl ester (3k) displayed better antiproliferative activity with IC₅₀ (50% inhibitory concentration) values of 5.90 ± 0.41 and 6.25 ± 0.37 µM toward HepG2 cells compared to cisplatin, while they exhibited lower cytotoxicity against HL-7702. Therefore, the 1,2,3-triazole-hybrids could be a promising strategy for the synthesis of antitumor diterpenoids and it also proved the essential role of 1,2,3-triazole moiety of DHAA in the biological activity.

The synthesis and antistaphylococcal activity of N-sulfonaminoethyloxime derivatives of dehydroabietic acid

A series of N-sulfonaminoethyloxime derivatives of dehydroabietic acid were synthesized and investigated for their antibacterial activity against Staphylococcus aureus Newman strain and multidrug-resistant strains (NRS-1, NRS-70, NRS-100, NRS-108 and NRS-271). Most of the target compounds having chloro, bromo, trifluoromethyl phenyl moiety exhibited potent in vitro antistaphylococcal activity. The meta-CF₃ phenyl derivative T23 showed the highest activity with MIC of 0.39-0.78 μg/mL against S. aureus Newman, while several analogues showed similar potent antibacterial activity with MIC values between 0.78 and 1.56 μg/mL against five multidrug-resistant S. aureus. The stability of T35 in plasma of SD rat and the cellular cytotoxicity were also evaluated.

Identification of a diverse synthetic abietane diterpenoid library and insight into the structure-activity relationships for antibacterial activity

A diverse natural product-like (NPL) synthetic abietane diterpenoid library containing 86 compounds were obtained and the SARs were studied based on their antibacterial potential. Further in vitro cytotoxic and in silico drug-like properties evaluation showed that the potent antibacterial compound 84 had good drug-like properties and displayed low cytotoxicity toward noncancerous mammalian cells, indicating the study of AA and DHAA might be a good starting point for the search of novel antimicrobial molecules. Future work should be focused on the optimization of their potency and selectivity.

The synthesis and antistaphylococcal activity of dehydroabietic acid derivatives: modifications at C12 and C7

A series of 7-N-acylaminoethyl/propyloxime derivatives of dehydroabietic acid were synthesized and investigated for their antibacterial activity against Staphylococcus aureus Newman strain and multidrug-resistant strains (NRS-1, NRS-70, NRS-100, NRS-108 and NRS-271). Most of the target compounds having trifluoromethyl phenyl/benzyl, halogen-substituted thiophenyl, benzothiophenyl or pyrrolyl moiety exhibited potent in vitro antibacterial activity. Among which, compounds 4m, 4x and 7j showed high antibacterial activity with minimum inhibitory concentration (MIC) values of 1.25-3.13 μg/mL against five multidrug-resistant S. aureus.