Three new lavandulylated flavonoids, (2S,2″S)-6-lavandulyl-7,4′-dimethoxy-5,2′-dihydroxylflavanone (1), (2S,2″S)-6-lavandulyl-5,7,2′,4′-tetrahydroxylflavanone (2), and (2″S)-5′-lavandulyl-2′-methoxy-2,4,4′,6′-tetrahydroxylchalcone (3), along with seven known compounds 4–10 were isolated from culture broth of Streptomyces sp. G248. Their structures were established by spectroscopic data analysis, including 1D and 2D nuclear magnetic resonance (NMR), and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The absolute configurations of 1–3 were resolved by comparison of their experimental and calculated electronic circular dichroism spectra. Compounds 1–3 exhibited remarkable antimicrobial activity. Whereas, two known compounds 4 and 5 exhibited inhibitory activity against Mycobacterium tuberculosis H37Rv with minimum inhibitory concentration (MIC) values of 6.0 µg/mL and 11.1 µg/mL, respectively.

The fruits of Amomun tsao-ko (Chinese black cardamom; Zingiberaceae) contain an abundance of essential oils, which have previously demonstrated significant antimicrobial activity. In our preliminary search for natural anti-tuberculosis agents, an acetone extract of A. tsao-ko (AAE) exhibited strong antibacterial activity against Mycobacterium tuberculosis H37Rv. Therefore, the aim of this study was to find the principal compounds in an AAE against M. tuberculosis. Nine aliphatic compounds (1–9) including a new compound (1, tsaokol B) and a new natural unsaturated aliphatic diester (6), together with three acyclic terpenoids (10–12), were isolated from an AAE by repetitive chromatography. The structures of the isolates were determined by spectroscopic data analysis. All isolates were evaluated for activity against M. tuberculosis H37Rv. Isolated compounds 1–6, and 11 had MICs ranging from 0.6–89 µg/mL. In contrast, compounds 7 to 10, and 12 had MICs that were >100 µg/mL. Tsaokol A (3) was the most active compound with MICs of 0.6 µg/mL and 1.4 µg/mL, respectively, against replicating and nonreplicating M. tuberculosis. These results are the first to illustrate the potency of tsaokol A (3) as a natural drug candidate with good selectivity for treating tuberculosis.

The bedaquiline (B), pretomanid (Pa), and linezolid (L) (BPaL) regimen is highly effective for drug-resistant tuberculosis (TB) but is limited by linezolid-associated toxicities, including myelosuppression and peripheral neuropathy. We evaluated omadacycline as a representative tetracycline-class protein synthesis inhibitor (PSI) to assess whether it can contribute functional activity within a BPa backbone. Omadacycline exhibited a minimum inhibitory concentration (MIC) of 2–4 μg/mL against M. tuberculosis H37Rv and 10–48 μg/mL against representatives of four global clades. Daily media replacement reduced the MIC against H37Rv to 0.29 μg/mL, suggesting antibiotic instability may underestimate in vitro potency. In vivo , subcutaneous administration of omadacycline (15 mg/kg) in BALB/c mice, yielding plasma exposures within the range of those reported for the approved 300-mg oral human dose, led to a 0.7-log ₁₀ reduction in lung colony-forming units (CFU) in both acute and chronic TB models. In combination therapy, 10-week treatment with BPa plus either linezolid (BPaL) or omadacycline (BPaO) further reduced lung CFU by ∼1 log ₁₀ relative to BPa alone, demonstrating the contribution of a PSI to regimen efficacy. Notably, BPaO and BPaL reduced relapse rates after 10 weeks of treatment to 43 and 23%, respectively, compared to 100% relapse in the BPa-only group. Together, these findings provide proof-of-concept evidence that omadacycline has in vivo antitubercular activity, achieves clinically relevant exposures, and can contribute functional PSI activity in combination regimens however, these results do not establish clinical equivalence with linezolid and support further evaluation of tetracycline-class agents in TB therapy.

Drug-resistant Mycobacterium tuberculosis (Mtb) remains a major global health challenge, prompting the need for new therapeutics targeting essential bacterial proteins. The caseinolytic protein C1 (ClpC1) is a promising drug target, and accurate measurement of its ATPase activity is critical for understanding drug mechanisms. We optimized a sensitive luminescence-based ATPase assay and evaluated ClpC1 constructs with various tag positions and truncations. N-terminal tagging significantly impaired enzymatic activity, whereas C-terminal tagging had no effect; truncated domains showed reduced activity compared to native full-length (FL) ClpC1. Using the native FL-ClpC1, we assessed ecumicin (ECU) and five analogs via ATPase activity and surface plasmon resonance (SPR), using rufomycin (RUF) and cyclomarin A (CYMA) as controls. RUF and CYMA bound tightly (K_D = 0.006–0.023 µM) and inhibited Mtb growth (MIC₉₀ = 0.02–0.094 µM) but modestly stimulated ATPase activity (≤2-fold). In contrast, ECU and its analogs strongly enhanced ATPase activity (4–9-fold) despite slightly weaker binding (K_D = 0.042–0.80 µM) and growth inhibition (MIC₉₀ = 0.19 µM). The partial correlation among AC₅₀, K_D, and MIC values highlights the complementary value of enzymatic, biophysical, and cellular assays. Our assay platform enables mechanistic characterization of ClpC1-targeting compounds and supports rational antitubercular drug development.