Aconitine linoleate, a natural lipo-diterpenoid alkaloid, stimulates anti-proliferative activity reversing doxorubicin resistance in MCF-7/ADR breast cancer cells as a selective topoisomerase IIα inhibitor

Aconitine linoleate (1) is a lipo-diterpenoid alkaloid, isolated from Aconitum sinchiangense W. T. Wang. The study aimed at investigating the anti-proliferative efficacy and the underlying mechanisms of 1 against MCF-7 and MCF-7/ADR cells, as well as obvious the safety evaluation in vivo. The cytotoxic activities of 1 were measured in vitro. Also, we investigated the latent mechanism of 1 by cell cycle analysis in MCF-7/ADR cells and topo I and topo IIα inhibition assay. Molecular docking is done by Discovery Studio 3.5 and Autodock vina 1.1.2. Finally, the acute toxicity of 1 was detected on mice. 1 exhibited significant antitumor activity against both MCF-7 and MCF-7/ADR cells, with IC50 values of 7.58 and 7.02 μM, which is 2.38 times and 5.05 times more active, respectively than etoposide in both cell lines, and being 9.63 times more active than Adriamycin in MCF-7/ADR cell lines. The molecular docking and the topo inhibition test found that it is a selective inhibitor of topoisomerase IIα. Moreover, activation of the damage response pathway of the DNA leads to cell cycle arrest at the G0G1 phase. Furthermore, the in vivo acute toxicity of 1 in mice displayed lower toxicity than aconitine, with LD50 of 2.2 × 105 nmol/kg and only slight pathological changes in liver and lung tissue, 489 times safer than aconitine. In conclusion, compared with aconitine, 1 has more significant anti-proliferative activity against MCF-7 and MCF-7/ADR cells and greatly reduces in vivo toxicity, which suggests this kind of lipo-alkaloids is powerful and promising antitumor compounds for breast cancer.

Synthesis and structure-activity relationship of lipo-diterpenoid alkaloids with potential target of topoisomerase IIα for breast cancer treatment

Aconitine linoleate (11) isolated from the Aconitum sinchiangense W. T. Wang exhibited significant anti-tumor activity. Based on this, a series of novel lipo-diterpenoid alkaloids were synthesized and evaluated for their anticancer activities against MCF-7 and MCF-7/ADR cell lines. Seventeen compounds, including 18-20, 22, 24-32, 36, 39, 41-42 possessed higher anti-proliferative activities (IC₅₀ < 20 μM) against MCF-7 cell lines, which were better than the reference drug etoposide (IC₅₀ = 18.01 ± 1.64 μM), among which compound 24 (IC₅₀ = 4.00 ± 0.30 μM) was found to be the most potent derivative, being 4.5-fold more active than etoposide. Meanwhile, eighteen compounds, including 18-22, 24, 26-32, 36, 38-39, 41-42 presented excellent activities (IC₅₀ < 20 μM) against MCF-7/ADR cell lines, better than etoposide (IC₅₀ = 35.48 ± 0.29 μM) and doxorubicin (IC₅₀ = 67.61 ± 6.5 μM). The most potent compound (19) was 13.5- and 25.7-fold more active than etoposide and doxorubicin against MCF-7/ADR cell lines, respectively. The structure-activity relationship (SAR) studies indicated that the 3-OH, 8-lipo, 14-benzene ring, and nitrogen atom with proper alkaline are crucial elements for anti-proliferative activity of target lipo-diterpenoid compounds. The proper length, the double bonds or di-fluoro-substituted at C-8 fatty acid chain, the para-donating electron group on 14-benzene group, and 13-OH are all favorable for the enhancement of anti-proliferative activities. In conclusion, the introduction of the 8-lipo group into aconitine leads to significant increase of anti-proliferative activity against MCF-7 and MCF-7/ADR cells, which suggests these kinds of lipo-alkaloids are powerful and promising antitumor compounds for breast cancer, especially for drug-resistant breast cancer.

Determination of the main naphthoquinones in Onosma hookeri Clarke. var. longiforum Duthie and its optimization of the ultrasound-assisted extraction using response surface methodology

In this study, besides isovaleryl shikonin, another shikonin derivative, tigloylshikonin, was also isolated from the roots of Onosma hookeri Clarke. var. longiforum Duthie as a main naphthoquinone constituent for the first time. Then optimization of the ultrasonic-assisted extraction was done by Box-Behnken design-response surface methodology on the basis of single-factor experiments. The optimized conditions were 72% (v/v) ethanol and the material to solution ratio was 1:37(g/mL) at 52 °C for 77 min. Under these conditions, the extraction yield of ethanol extract was 36.74 ± 0.32%, the contents of isovaleryl shikonin and tigloylshikonin reached 0.094 ± 0.003% and 0.223 ± 0.006%, respectively. Notably, in that optimized condition, the yield of isovaleryl shikonin increased by approximately 7.64-fold than the previous report. In the in vitro antioxidant activity assay, the optimal ethanol extract exhibited similar 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity as butylated hydroxy toluene (BHT), but slightly weaker 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) scavenging activity and total antioxidant capacity than that of BHT. However, the active polar fraction, the ethyl acetate fraction, which is enriched with naphthoquinone constituents, performs as a better antioxidant agent than BHT. Therefore, both of them could be considered as a naturally sourced antioxidants compared to commercially available synthetic drugs. PRACTICAL APPLICATION: Onosma hookeri Clarke. var. longiforum Duthie, a traditional Chinese medicine and food item, has been in use since a long time. A systematic determination of the main naphthoquinones, and antioxidant capacity of the naphthoquinones-enriched ethanol extract and different polar fractions, was carried out in the present study. The results may provide theoretical basis for the claim that naphthoquinones-enriched ethanol extract and ethyl acetate fraction from the roots of Onosma hookeri Clarke. var. longiforum Duthie could be used as potential natural antioxidants in the pharmaceutical, food, and cosmetic industries.

Evaluation of antioxidant and anticancer activities of naphthoquinones-enriched ethanol extracts from the roots of Onosma hookeri Clarke. var. longiforum Duthie

In this study, the optimal naphthoquinones-enriched ethanol extract from the roots of Onosma hookeri Clarke. var. longiforum Duthie (OHC-LD) was obtained under an optimal condition (69% ethanol, material to solution ratio of 27:1 at 60℃ for 59 min) by the ultrasound-assisted extraction, according to four-variable three-level Box-Behnken design-response surface methodology. The experimental yield of ethanol extract was 42.08 ± 0.65%, and the contents of naphthoquinones reached to 1.07 ± 0.004%. The optimal extract exhibited similar scavenging activity against ABTS (2,2'-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid) radical as BHT(butylated hydroxytoluene) at 1,250 µg/ml, and better DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activity than BHT at 250 µg/ml. However, the optimal ethanol extract was not sensitive to MCF-7 cell line ( IC50 of 321.849 µg/ml). The results revealed the naphthoquinones-enriched ethanol extract from the roots of OHC-LD had could be used as a potential natural antioxidant.

A comprehensive review of topoisomerase inhibitors as anticancer agents in the past decade

The topoisomerase enzymes play an important role in DNA metabolism, and searching for enzyme inhibitors is an important target in the search for new anticancer drugs. Discovery of new anticancer chemotherapeutical capable of inhibiting topoisomerase enzymes is highlighted in anticancer research. Therefore, biologists, organic chemists and medicinal chemists all around the world have been identifying, designing, synthesizing and evaluating a variety of novel bioactive molecules targeting topoisomerase. This review summarizes types of topoisomerase inhibitors in the past decade, and divides them into nine classes by structural characteristics, including N-heterocycles compounds, quinone derivatives, flavonoids derivatives, coumarin derivatives, lignan derivatives, polyphenol derivatives, diterpenes derivatives, fatty acids derivatives, and metal complexes. Then we discussed the application prospect and development of these anticancer compounds, as well as concluded parts of their structural-activity relationships. We believe this review would be invaluable in helping to further search potential topoisomerase inhibition as antitumor agent in clinical usage.

Two decades of advances in diterpenoid alkaloids with cytotoxicity activities

The important pharmacological activities and structural complexity of diterpenoid alkaloids have long stimulated strong scientific interest; some of these naturally abundant compounds have been reported to be highly promising for treating cancer.

Effect of a grain challenge on ruminal, urine, and fecal pH, apparent total-tract starch digestibility, and milk composition of Holstein and Jersey cows

The effects of a grain challenge on ruminal, urine, and fecal pH, apparent total-tract starch digestibility, and milk composition were determined. Six Holstein cows, 6 rumen-cannulated Holstein cows, and 6 Jersey cows were used in a replicated 3 × 3 Latin square design balanced to measure carryover effects. Periods (10 d) were divided into 4 stages (S): S1, d 1 to 3, served as baseline with regular total mixed ration ad libitum; S2, d 4, served as restricted feeding, with cows offered 50% of the total mixed ration fed on S1 (dry matter basis); S3, d 5, a grain challenge was performed, in which cows were fed total mixed ration ad libitum and not fed (CON) or fed an addition of 10% (MG) or 20% (HG) pellet wheat-barley (1:1) top-dressed onto the total mixed ration, based on dry matter intake obtained in S1; S4, d 6 to 10, served as recovery stage with regular total mixed ration fed ad libitum. Overall, cows had a quadratic treatment effect for milk yield where CON (22.6 kg/d) and HG (23.5 kg/d) had lower milk yield than cows in MG (23.7 kg/d). Jersey cows had a quadratic treatment effect for dry matter intake where cows in CON (13.2 kg/d) and HG (12.4 kg/d) had lower dry matter intake than cows in MG (14 kg/d). Holstein cows had a linear treatment effect for dry matter intake (17.7, 18.4, and 18.6 kg/d for CON, MG, and HG, respectively). Rumen pH for the rumen-cannulated cows had a linear treatment effect (6.45, 6.35, and 6.24 for CON, MG, and HG, respectively). Cows in HG spent more time with rumen pH below 5.8 (4.33 h) than MG (2 h) or CON (2.17 h) as shown by the quadratic treatment effect. Holstein cows in HG (8.46) had lower urine pH than MG (8.51) or CON (8.54) as showed by the linear treatment effect for urine pH. Apparent total-tract starch digestibility had a tendency for a linear treatment effect on S3 (97.62 ± 1.5, 97.47 ± 1.5, and 91.84 ± 1.6%, for CON, MG, and HG, respectively). Fecal pH was associated with rumen pH depression as early as 15 h after feeding for Holstein cows. In conclusion, a grain challenge reduced urine pH in Holstein cows but not in Jersey cows. Holstein cows' health were not affected when rumen pH was depressed. A potentially useful link between rumen pH and systemic (urine) pH within 2 h after feeding was quantified in Holstein cows.