Cytotoxic Potential of Diterpenoids from the Genus Croton Against Breast Cancer Cell Lines: A Comprehensive Review

Abstract

Globally, breast cancer is one of the most prevalent tumors in women and remains a major concern due to its high mortality rate. Although treatment options for this disease have evolved over the years, there are still many cases of recurrence and metastasis. In this context, considering the importance of evaluating less aggressive and more efficient therapeutic alternatives to aid in the treatment of breast cancer, the present study critically discusses the cytotoxic effects of diterpenoids isolated from Croton species (Euphorbiaceae). The articles were retrieved from different databases, from the first report published in 2005 to October 2025. A total of 115 diterpenoids were isolated from 15 Croton species and investigated against different breast cancer cell lines (MDA-MB-231, MCF-7, and MDA-MB-468). These compounds mainly belong to the kaurane group (40%), followed by clerodane (14%), tigliane (12%), and abietane (10%). Of this total, only 25 compounds showed promising results (IC₅₀ = < 10 µM). The mechanisms of action of the compounds crokokaugenoid A, kongensin A, kongensin D, ent-16β,17α-dihydroxykaurane, and lauicyclone A have been reported. These compounds likely act by inducing apoptosis, autophagy, cell cycle arrest, inhibition of cell migration and invasion, and DNA fragmentation in breast cancer cell lines. To date, no randomized clinical trials have been conducted using Croton diterpenoids for the treatment of breast cancer. Therefore, further studies on the modulation of the immune response by these natural products are essential to better understand their immunotherapeutic activity in the tumor microenvironment during breast cancer progression.

1. Introduction

Breast cancer is one of the most prevalent tumors in women and remains a major challenge for global health. Its occurrence is associated with several factors, such as genetic mutations, late menopause, and obesity [1]. Statistical data from 2022 showed that breast cancer in women was the first or second most commonly diagnosed cancer in 183 out of 185 countries, with a high mortality rate in 169 countries [2]. Additionally, projections for 2050 estimate the occurrence of 3.2 million new cases and 1.1 million deaths from breast cancer worldwide [2]. Mortality rates from this disease can be influenced by genetic factors and the interaction between genetic predispositions and the environment [3]. Although developed countries continually update data on new cancer cases, most developing countries have limited information on this disease [4].

Over the years, breast cancer treatment has evolved from simple surgical resection to more modern therapeutic alternatives, including chemotherapy, radiotherapy, targeted therapy, and immunotherapy [5]. However, despite continuous advances in treatment methods for this disease, recurrence and metastasis remain major concerns [6]. In this context, there is an urgent need to develop more targeted, efficient, and less aggressive treatment approaches to halt the progression of breast cancer. Natural products and their derivatives can be considered promising alternatives for the development of new drugs against breast cancer due to their low toxicity and reduced side effects [7].

Diterpenoids are a large class of organic compounds in the terpene family that exert their cytotoxic effects through a wide range of mechanisms of action [8], including antiproliferative action, inhibition of angiogenesis, inhibition of tumor metastasis, and induction of cell death [9]. Paclitaxel, better known as Taxol^®, is an example of a natural diterpene derived from the bark of Taxus brevifolia Nutt., and its mechanism of action is associated with attacking the microtubules of cancer cells [10]. In addition to their occurrence in T. brevifolia, diterpenes are also considered a class of taxonomic markers of the Euphorbiaceae family, occurring in several genera such as Croton, Euphorbia, and Jatropha [11,12,13,14,15]. Croton comprises approximately 1200 species that occur in habitats ranging from dry to humid vegetation in the tropics and subtropics worldwide [16].

Different groups of diterpenoids, such as labdane [17], pimarane [18], abietane [19], tigliane [20], clerodane [21,22], and kaurane [23,24] isolated from Croton species, have demonstrated potential cytotoxic activity in experimental studies. Only one review study reported the cytotoxic potential of diterpenoids from Croton tonkinensis [15]; however, to date, no literature reviews have been found on the cytotoxic effects of diterpenoids isolated from various representatives of this genus against breast cancer cell lines. In this context, considering the importance of evaluating less aggressive and more efficient therapeutic alternatives to aid in the treatment of breast cancer, the present study critically discusses the cytotoxic effects of diterpenoids isolated from Croton species.

2. Data Sources and Retrieval Strategy

2.1. Databases

The articles were retrieved from SciELO, Scopus, Web of Science, ScienceDirect, and PubMed databases. The following keywords were defined and combined to aid in article searches: “anticancer”, “diterpenes”, “diterpenoids”, “cytotoxicity”, “Croton”, “antiproliferative”, “antitumor”, “breast cancer”, “MDA-MB-231”, “MCF-7”, and “MDA-MB-468”.

2.2. Inclusion and Exclusion Criteria

Only articles on the topic published from the first report by Morales et al. [25] until October 2025 were considered. Specifically, to be included in this review, studies should present detailed methodological information on the extraction, isolation, and NMR elucidation process of diterpenoids from Croton species, as well as the cytotoxic investigation of the compounds against different breast cancer cell lines (MDA-MB-231, MCF-7, and MDA-MB-468). Literature review studies, book chapters, e-books, undergraduate theses, Master’s theses, PhD theses, and abstracts published in proceedings of scientific events were excluded [26]. In addition, articles that reported the cytotoxic potential of semi-synthetic diterpenoids or that were not directly isolated from Croton species were excluded. All scientific names of the plants were checked on the World Flora Online (WFO) Plant List platform (https://wfoplantlist.org/ (Accessed on 20 March 2026)).

2.3. Data Screening and Information Categorization

Initially, 982 documents were found in the databases. Subsequently, a pre-selection was carried out, where the authors read the titles, abstracts, and keywords to eliminate any documents that did not meet the pre-established inclusion criteria. Following this pre-selection, a complete reading of 421 documents was carried out. Finally, 25 articles were included in this study. The results were organized and described according to the different diterpenoid groups of Croton: (1) Abietane, (2) Clerodane, (3) Kaurane, (4) Labdane, (5) Tigliane, (6) Casbane, (7) Cembrane, (8) Crotofolane, (9) Pimarane, and (10) Crotinsulidane.

2.4. Data Analysis

The results reported in scientific articles on the cytotoxic activity of Croton diterpenoids against breast cancer cell lines (MDA-MB-231, MCF-7, and MDA-MB-468) were analyzed based on Brahemi et al. [27]. Following these criteria, isolated compounds that showed IC₅₀ values (concentration that causes 50% cell death) > 10 μM were considered inactive.

3. Cytotoxic Potential of Diterpenoids

A total of 115 diterpenoids were isolated from 15 species of Croton and investigated against different breast cancer cell lines. Most of these compounds belong to the kaurane group (40%), followed by clerodane (14%), tigliane (12%), and abietane (10%) (Figure 1). These compounds were isolated from C. kongensis Gagnep., C. laevigatus Vahl, C. caudatus Geiseler, C. oligandrus Pierre ex Hutch., C. oblongus Burm.f., C. oblongifolius (= C. persimilis Müll.Arg.), C. laui Merr. & F.P.Metcalf, C. tonkinensis (= C. kongensis Gagnep.), C. mekongensis Gagnep., C. malambo H.Karst., C. caracasanus Pittier, C. stipuliformis (= C. costatus Kunth), C. tiglium L., C. damayeshu Y.T.Chang, and C. insularis Baill. The leaves and branches were the main plant parts used for the extraction and isolation of diterpenoids. Regarding the main cell lines evaluated in the cytotoxicity assays, it was observed that MDA-MB-231 and MCF-7 stood out, while MDA-MB-468 was the least tested. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was the most widely used to evaluate the cytotoxic potential of Croton diterpenoids.

3.1. Abietane

A total of 11 compounds belonging to the abietane group were isolated from Croton species and evaluated against breast cancer cell lines (

Table 1. Cytotoxicity of abietane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(1) Crokoabiegenoid A	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(2) Crokoabiegenoid B	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(3) Corokongenolide A	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(4) Crokongendin B	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = 1.77 μM (MDA-MB-231), IC50 = 0.116 μM (MDA-MB-468), IC50 = 1.24 μM (MCF-7)	Fan et al. [24]
	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 14.9 μM (MDA-MB-231), IC50 = 4.93 μM (MCF-7)	Zhu et al. [28]
(5) Crotolaevigatone B	Croton laevigatus	Leaves, branches	MDA-MB-231	MTT	IC50 = 33.4 µM	Song et al. [19]
(6) Crotolaevigatone G	Croton laevigatus	Leaves, branches	MDA-MB-231	MTT	IC50 = 32.7 µM	Song et al. [19]
(7) Crotontomentosin A	Croton caudatus	Leaves, branches	MDA-MB-231	MTT	IC50 = 54.1 µM	Song et al. [29]
(8) Crotontomentosin B	Croton caudatus	Leaves, branches	MDA-MB-231	MTT	IC50 = 28.7 µM	Song et al. [29]
(9) Crotontomentosin C	Croton caudatus	Leaves, branches	MDA-MB-231	MTT	IC50 = > 100 µM	Song et al. [29]
(10) Crotontomentosin	Croton caudatus	Leaves, branches	MDA-MB-231	MTT	IC50 = 49.3 µM	Song et al. [29]
(11) 15-Hydroxy-7-oxoabieta-8,11,13-triene	Croton caudatus	Leaves, branches	MDA-MB-231	MTT	IC50 = 69.8 µM	Song et al. [29]

MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.

and Figure 2). Only compound 4 (crokongendin B) isolated from C. kongensis branches showed high activity when evaluated against MDA-MB-231 (IC₅₀ = 1.77 µM), MDA-MB-468 (IC₅₀ = 0.116 µM), and MCF-7 (IC₅₀ = 1.24 µM) [24].

3.2. Clerodane

Although 16 clerodane compounds were isolated from Croton species (

Table 2. Cytotoxicity of clerodane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(12) Crocleropene A	Croton caudatus	Leaves, branches	MCF-7	MTT	IC50 = 35.8 µM	Zou et al. [22]
(13) Crocleropene B	Croton caudatus	Leaves, branches	MCF-7	MTT	IC50 = 40.2 µM	Zou et al. [22]
(14) 12-epi-Crotocorylifuran	Croton oligandrus	Stem bark	MCF-7	MTT	IC50 = > 200 μM	Guetchueng et al. [30]
(15) 12-epi-Megalocarpodolide D	Croton oligandrus	Stem bark	MCF-7	MTT	IC50 = 171.3 μM	Guetchueng et al. [30]
(16) Megalocarpodolide D	Croton oligandrus	Stem bark	MCF-7	MTT	IC50 = 136.2 µM	Guetchueng et al. [30]
(17) Laevifin A	Croton oblongus	Stem bark	MCF-7	MTT	IC50 = 102 µM	Aziz et al. [21]
(18) Laevifin B	Croton oblongus	Stem bark	MCF-7	MTT	IC50 = 115 µM	Aziz et al. [21]
(19) Laevifin G	Croton oblongus	Stem bark	MCF-7	MTT	IC50 = 106 µM	Aziz et al. [21]
(20) Methyl 15,16-epoxy-3,13(16),14-ent-clerodatrien-18,19-olide-17-carboxylate	Croton oblongifolius	Root	MDA-MB-231	Colorimetric assay	IC50 = 29.0 µM	Youngsa-ad et al. [31]
(21) Dimethyl-12-oxo-3,13(16),14-ent-clerodatriene-17,18-dicarboxylate	Croton oblongifolius	Root	MDA-MB-231	Colorimetric assay	IC50 = 27.0 µM	Youngsa-ad et al. [31]
(22) Nasimalun A	Croton oblongifolius	Root	MDA-MB-231	Colorimetric assay	IC50 = 40.0 µM	Youngsa-ad et al. [31]
(23) Nasimalun B	Croton oblongifolius	Root	MDA-MB-231	Colorimetric assay	IC50 = 26.0 µM	Youngsa-ad et al. [31]
(24) Levatin	Croton oblongifolius	Root	MDA-MB-231	Colorimetric assay	IC50 = > 50 µM	Youngsa-ad et al. [31]
(25) (−)-Hardwickiic acid	Croton oblongifolius	Root	MDA-MB-231	Colorimetric assay	IC50 = 28.0 µM	Youngsa-ad et al. [31]
(26) 15-Hydroxy-cis-ent-cleroda-3,13(E)-diene	Croton oblongifolius	Root	MDA-MB-231	Colorimetric assay	IC50 = 25.0 µM	Youngsa-ad et al. [31]
(27) Launine K	Croton laui	Aerial part	MCF-7	Colorimetric assay	IC50 = 62.5 µM	Youngsa-ad et al. [31]

MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.

and Figure 3), none of these compounds showed activity (IC₅₀ = > 10 µM) against the MCF-7 and MDA-MB-231 cell lines evaluated in cytotoxicity studies.

3.3. Kaurane

Several molecules belonging to the kaurane group have been isolated from Croton species and evaluated for their cytotoxic effect (

Table 3. Cytotoxicity of kaurane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(28) Crokokaugenoid A	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 2.52 μM (MDA-MB-231), IC50 = 3.30 μM (MCF-7)	Zhu et al. [28]
(29) Crokokaugenoid B	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(30) Crokokaugenoid C	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(31) Crokokaugenoid D	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 15.43 μM (MDA-MB-231), IC50 = 13.21 μM (MCF-7)	Zhu et al. [28]
(32) Crokokaugenoid E	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 6.57 μM (MDA-MB-231), IC50 = 9.55 μM (MCF-7)	Zhu et al. [28]
(33) Crokokaugenoid F	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(34) Crokokaugenoid G	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(35) Crokokaugenoid H	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(36) (4α)-15-Oxokaur-16-en-18-oic acid	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(37) ent-19-Hydroxykaur-16-en-15-one	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 18.02 μM (MDA-MB-231), IC50 = 19.48 μM (MCF-7)	Zhu et al. [28]
(38) ent-19-Oxo-kaur-16-en-15-one	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(39) Kongensin E	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 7.89 μM (MDA-MB-231), IC50 = 3.75 μM (MCF-7)	Zhu et al. [28]
(40) Serrin F	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 6.35 μM (MDA-MB-231), IC50 = 6.34 μM (MCF-7)	Zhu et al. [28]
(41) Isolushinin D	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 8.15 μM (MDA-MB-231), IC50 = 9.47 μM (MCF-7)	Zhu et al. [28]
(42) 15β-Hydroxy-(−)-kaur-16-en19-oic acid	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(43) Croyanhuin A	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 2.62 μM (MDA-MB-231), IC50 = 2.97 μM (MCF-7)	Zhu et al. [28]
(44) Kongeniod C	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 10.65 μM (MDA-MB-231), IC50 = 8.88 μM (MCF-7)	Zhu et al. [28]
(45) Kongensin B	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 9.38 μM (MDA-MB-231), IC50 = 7.75 μM (MCF-7)	Zhu et al. [28]
(46) ent-8,9-seco-1β,7α-Dihydroxy-8(14)-en-9,15-dione	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(47) ent-7β-Hydroxy-16-kauren-15-one	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 1.47 µg/mL	Kuo et al. [33]
(48) ent-7β-Hydroxy-15-oxokaur-16-en-18-yl acetate	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 0.65 µg/mL	Kuo et al. [33]
(49) ent-Kaur-16-en-15-one 18-oic acid	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 2.69 µg/mL	Kuo et al. [33]
(50) ent-18-Acetoxykaur-16-en-15-one	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 6.11 µg/mL	Kuo et al. [33]
(51) ent-1β-Acetoxy-7α,14β-dihydroxykaur-16-en15-one	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 0.94 µg/mL	Kuo et al. [33]
	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 5.02 μM (MDA-MB-231), IC50 = 6.52 μM (MCF-7)	Zhu et al. [28]
(52) ent-7α,14β-Dihydroxykaur-16-en-15-one	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 0.75 µg/mL	Kuo et al. [33]
	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 2.96 μM (MDA-MB-231), IC50 = 3.36 μM (MCF-7)	Zhu et al. [28]
(53) ent-18-Hydroxykaur-16-en-15-one	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 4.31 µg/mL	Kuo et al. [33]
(54) ent-7β-Hydroxy-15-oxokaur-16-en-18-ol	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 0.98 µg/mL	Kuo et al. [33]
	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 14.03 μM (MDA-MB-231), IC50 = 14.30 μM (MCF-7)	Zhu et al. [28]
(55) ent-18-Acetoxy-7α,14β-dihydroxykaur-16-en-15-one	Croton tonkinensis	Whole plant	MCF-7	MTS	EC50 = 1.98 µg/mL	Kuo et al. [33]
(56) Crokongendin A	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = 0.153 μM (MDA-MB-231), IC50 = 0.116 μM (MDA-MB-468), IC50 = 0.248 μM (MCF-7)	Fan et al. [24]
(57) Euphoranginone D	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = > 5 µM (MDA-MB-231), IC50 = > 5 µM (MDA-MB-468), IC50 = > 5 μM (MCF-7)	Fan et al. [24]
(58) ent-Kaurane-3-oxo-16β,17-diol	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = > 5 µM (MDA-MB-231), IC50 = > 5 µM (MDA-MB-468), IC50 = > 5 μM (MCF-7)	Fan et al. [24]
(59) ent-16β-H-3-Oxokauran-17-ol	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = > 5 µM (MDA-MB-231), IC50 = > 5 µM (MDA-MB-468), IC50 = > 5 μM (MCF-7)	Fan et al. [24]
(60) Kongensin D	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = 0.0783 µM (MDA-MB-231), IC50 = 0.0716 µM (MDA-MB-468), IC50 = 0.113 μM (MCF-7)	Fan et al. [24]
	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 17.74 µM (MDA-MB-231), IC50 = 9.82 μM (MCF-7)	Zhu et al. [28]
(61) Kongeniod B	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = 0.185 µM (MDA-MB-231), IC50 = 0.121 µM (MDA-MB-468), IC50 = 0.215 μM (MCF-7)	Fan et al. [24]
(62) Kongensin A	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = 0.177 µM (MDA-MB-231), IC50 = 0.228 µM (MDA-MB-468), IC50 = 0.120 μM (MCF-7)	Fan et al. [24]
	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 3.27 µM (MDA-MB-231), IC50 = 5.83 μM (MCF-7)	Zhu et al. [28]
(63) Kongensin F	Croton kongensis	Branches	MDA-MB-231, MDA-MB-468, MCF-7	MTT	IC50 = 0.677 µM (MDA-MB-231), IC50 = 0.236 µM (MDA-MB-468), IC50 = 0.266 μM (MCF-7)	Fan et al. [24]
	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = 5.23 µM (MDA-MB-231), IC50 = 5.15 μM (MCF-7)	Zhu et al. [28]
(64) Crotonkinensin C	Croton tonkinensis	Leaves	MDA-MB-231, MCF-7	MTT	IC50 = > 30 µM (MDA-MB-231), IC50 = > 30 μM (MCF-7)	Thuong et al. [32]
(65) Crotonkinensin D	Croton tonkinensis	Leaves	MDA-MB-231, MCF-7	MTT	IC50 = 22.0 µM (MDA-MB-231), IC50 = 9.4 μM (MCF-7)	Thuong et al. [32]
(66) Crotonmekongenin A	Croton mekongensis	Aerial parts	MDB-MB-231	SRB	ED50 = 0.55 µg/mL	Udomthawee et al. [23]
(67) ent-16β,17α-Dihydroxykaurane	Croton malambo	Bark	MCF-7	MTT	IC50 = 12.5 µg/mL	Morales et al. [25]
(68) Crotonkinensin E	Croton tonkinensis	Leaves	MCF-7	MTT	IC50 = 24.1 µg/mL	Quan et al. [34]
(69) ent-1β-Acetoxy-7α,14β-dihydroxykaur-16-en-15-one	Croton tonkinensis	Leaves	MCF-7	MTT	IC50 = 7.3 µg/mL	Quan et al. [34]
(70) ent-18-Acetoxy-7α-hydroxykaur-16-en-15-one	Croton tonkinensis	Leaves	MCF-7	MTT	IC50 = 6.0 µg/mL	Quan et al. [34]
	Croton kongensis	Branches, leaves	MDA-MB-231, MCF-7	MTT	IC50 = 4.32 µM (MDA-MB-231), IC50 = 4.21 μM (MCF-7)	Zhu et al. [28]
(71) ent-18-Acetoxy-7α,14β-dihydroxykaur-16-en-15-one	Croton tonkinensis	Leaves	MCF-7	MTT	IC50 = 4.5 µg/mL	Quan et al. [34]
	Croton kongensis	Branches, leaves	MDA-MB-231, MCF-7	MTT	IC50 = 2.86 µM (MDA-MB-231), IC50 = 3.87 μM (MCF-7)	Zhu et al. [28]
(72) Caracasine	Croton caracasanus	Flowers	MCF-7	MTT	IC50 = 15.7 µg/mL	Suárez et al. [35]
(73) Caracasine acid	Croton caracasanus	Flowers	MCF-7	MTT	IC50 = 6.0 µg/mL	Suárez et al. [35]

MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. MTS: colorimetric assay. SRB: sulforhodamine B.

and Figure 4). Among these, compounds 28 (crokokaugenoid A), 32 (crokokaugenoid E), 39 (kongensin E), 40 (serrin F), 41 (isolushinin D), 43 (croyanhuin A), 44 (kongeniod C), 45 (kongensin B), 51 (ent-1β-acetoxy-7α,14β-dihydroxykaur-16-en15-one), 52 (ent-7α,14β-dihydroxykaur-16-en-15-one), 70 (ent-18-acetoxy-7α-hydroxykaur-16-en-15-one), and 71 (ent-18-acetoxy-7α,14β-dihydroxykaur-16-en-15-one) isolated from the leaves and branches of C. kongensis were active (IC₅₀ = < 10 µM) against the MDA-MB-231 and MCF-7 cell lines [28]. In another study, Thuong et al. [32] reported that compound 65 (crotonkinensin D) isolated from C. tonkinensis leaves also exhibited a promising cytotoxic effect against MCF-7 cells (IC₅₀ = 9.4 µM). Compounds 56 (crokongendin A), 60 (kongensin D), 61 (kongeniod B), 62 (kongensin A), and 63 (kongensin F) isolated from C. kongensis branches, were also tested against MDA-MB-231, MDA-MB-468, and MCF-7 cells and showed IC₅₀ values lower than 10 µM, indicating that they are promising against breast cancer [24].

3.4. Labdane

Only three compounds belonging to the labdane group were isolated from C. stipuliformis and C. laui and evaluated against the MCF-7 cell line (

Table 4. Cytotoxicity of labdane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(74) 12E-3,4-seco-Labda-4(18),8(17),12,14-tetraen-3-oic acid methyl ester	Croton stipuliformis	Stem bark	MCF-7	MTT	LC50 = 24.8 µg/mL	Franco et al. [17]
(75) 12E-3,4-seco-Labda-4(18),8(17),12,14-tetraen-3-oic acid	Croton stipuliformis	Stem bark	MCF-7	MTT	LC50 = 16.0 µg/mL	Franco et al. [17]
(76) Labdinine N	Croton laui	Aerial parts	MCF-7	MTT	IC50 = > 50 μM	Yang et al. [36]

MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.

and Figure 5). None of these compounds showed promising results.

3.5. Tigliane

A total of 14 compounds belonging to the tigliane group were isolated from Croton species and tested against breast cancer cells (

Table 5. Cytotoxicity of tigliane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(77) Crotonol A	Croton tiglium	Leaves	MCF-7	MTT	IC50 = 17.60 µM	Wang et al. [38]
(78) Crotonol B	Croton tiglium	Leaves	MCF-7	MTT	IC50 = > 50 µM	Wang et al. [38]
(79) Crotusin A	Croton caudatus	Leaves, branches	MCF-7	MTS	IC50 = 9.56 µM	Chen et al. [20]
(80) Crotusin B	Croton caudatus	Leaves, branches	MCF-7	MTS	IC50 = 1.49 µM	Chen et al. [20]
(81) Crotusin C	Croton caudatus	Leaves, branches	MCF-7	MTS	IC50 = 0.49 µM	Chen et al. [20]
(82) 12-O-Acetylphorbol-13-isobutyrate	Croton tiglium	Aerial parts	MCF-7	CCK-8	IC50 = 13 µM	Wang et al. [39]
(83) 12-O-benzoylphorbol-13-(2-methyl)butyrate	Croton tiglium	Leaves, branches	MCF-7	CCK-8	IC50 = 20 µM	Wang et al. [39]
(84) 12-O-Tiglyl-7-oxo-5-ene-phorbol-13-(2-methylbutyrate)	Croton tiglium	Aerial parts	MCF-7	CCK-8	IC50 = 20 µM	Wang et al. [39]
(85) 13-O-(2-Metyl)butyryl-4-deoxy-4ɑ-phorbol	Croton tiglium	Leaves, branches	MCF-7	CCK-8	IC50 = 24 µM	Wang et al. [39]
(86) 12-O-Tiglylphorbol-13-isobutyrate	Croton tiglium	Leaves, branches	MCF-7	CCK-8	IC50 = > 50 µM	Wang et al. [39]
(87) Tiglin A	Croton tiglium	Leaves, branches	MCF-7	CCK-8	IC50 = > 50 µM	Wang et al. [39]
(88) 12-O-(2-Methyl)butyryl-4-deoxy-4α-phorbol-13-decanoate	Croton damayeshu	Whole plant	MDA-MB-231	MTT	IC50 = 1.992 µM	Jia et al. [37]
(89) 12-O-Tiglyl-4α-deoxyphorbol-13-(2-methyl)-butyrate	Croton damayeshu	Whole plant	MDA-MB-231	MTT	IC50 = 16.41 µM	Jia et al. [37]
(90) 12-O-Tiglylphorbol-13-(2-methyl)butyrate	Croton damayeshu	Whole plant	MDA-MB-231	MTT	IC50 = 14.59 µM	Jia et al. [37]

MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. MTS: colorimetric assay. CCK-8: Cell Counting Kit-8.

and Figure 6). According to Chen et al. [20], compounds 79 (crotusin A), 80 (crotusin B), and 81 (crotusin C) isolated from the leaves and branches of C. caudatus exhibited IC₅₀ values of only 9.56, 1.49, and 0.49 µM against MCF-7 cells, respectively. In another study, Jia et al. [37] reported that compound 88 (12-O-(2-metil)butiril-4-desoxi-4y-forbol-13-decanoato) isolated from C. damayeshu also showed activity (IC₅₀ = 1.992 µM) against MDA-MB-231 cells.

3.6. Casbane

Compounds 94 (EBC-304) and 95 (EBC-320), belonging to the casbane group, were isolated from the aerial parts of C. insularis and exhibited promising cytotoxic activity, with IC₅₀ values of only 5 and 3 µM, respectively, against MCF-7 cells [40] (

Table 6. Cytotoxicity of casbane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(91) EBC-131	Croton insularis	Stem	MCF-7	MTS	IC50 = 60 µM	Maslovskaya et al. [41]
(92) EBC-180	Croton insularis	Stem	MCF-7	MTS	IC50 = 18 µM	Maslovskaya et al. [41]
(93) EBC-181	Croton insularis	Stem	MCF-7	MTS	IC50 = 30 µM	Maslovskaya et al. [41]
(94) EBC-304	Croton insularis	Aerial parts	MCF-7	MTS	IC50 = 5 µM	Maslovskaya et al. [40]
(95) EBC-320	Croton insularis	Aerial parts	MCF-7	MTS	IC50 = 3 µM	Maslovskaya et al. [40]

MTS: colorimetric assay.

and Figure 7).

3.7. Cembrane

A total of six cembrane compounds were isolated from the aerial parts of C. laui and evaluated for their cytotoxic potential. However, all of these compounds showed IC₅₀ values greater than 50 μM and were considered inactive against MCF-7 cells (

Table 7. Cytotoxicity of cembrane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(96) Launine O	Croton laui	Aerial parts	MCF-7	MTT	IC50 = > 50 μM	Yang et al. [36]
(97) Launine P	Croton laui	Aerial parts	MCF-7	MTT	IC50 = > 50 μM	Yang et al. [36]
(98) (1S,4R,13S)-Cembra-2E,7E,11-E-trien-4,13-diol	Croton laui	Aerial parts	MCF-7	MTT	IC50 = > 50 μM	Yang et al. [36]
(99) Sarcophytol T	Croton laui	Aerial parts	MCF-7	MTT	IC50 = > 50 μM	Yang et al. [36]
(100) Serratol	Croton laui	Aerial parts	MCF-7	MTT	IC50 = > 50 μM	Yang et al. [36]
(101) Nephthenol	Croton laui	Aerial parts	MCF-7	MTT	IC50 = > 50 μM	Yang et al. [36]

MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.

and Figure 8).

3.8. Crotofolane

As observed for cembrane, compounds belonging to the crotofolane group isolated from Croton species also did not show any relevant cytotoxic effect against the MDA-MB-231 and MCF-7 cell lines (

Table 8. Cytotoxicity of crotofolane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(102) Crokocrotogenoid A	Croton kongensis	Leaves, branches	MDA-MB-231, MCF-7	MTT	IC50 = > 20 μM (MDA-MB-231), IC50 = > 20 μM (MCF-7)	Zhu et al. [28]
(103) EBC-162	Croton insularis	Stem	MCF-7	MTS	IC50 = 30 µg/mL	Maslovskaya et al. [42]
(104) EBC-233	Croton insularis	Stem	MCF-7	MTS	IC50 = 20 µg/mL	Maslovskaya et al. [42]
(105) EBC-300	Croton insularis	Stem	MCF-7	MTS	IC50 = 100 µg/mL	Maslovskaya et al. [42]
(106) EBC-240	Croton insularis	Stem	MCF-7	MTS	IC50 = 50 µg/mL	Maslovskaya et al. [42]
(107) EBC-241	Croton insularis	Stem	MCF-7	MTS	IC50 = 40 µg/mL	Maslovskaya et al. [42]

MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. MTS: colorimetric assay.

and Figure 9).

3.9. Pimarane

Compounds belonging to the pimarane group were isolated from the bark of C. insularis and the leaves of C. laui and evaluated against MCF-7 cells. The IC₅₀ values obtained were greater than 10 µM and, therefore, considered inactive against this specific cell line (

Table 9. Cytotoxicity of pimarane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(108) EBC-325	Croton insularis	Stem	MCF-7	MTS	IC50 = 20 µg/mL	Maslovskaya et al. [18]
(109) EBC-326	Croton insularis	Stem	MCF-7	MTS	IC50 = 14 µg/mL	Maslovskaya et al. [18]
(110) EBC-327	Croton insularis	Stem	MCF-7	MTS	IC50 = 10 µg/mL	Maslovskaya et al. [18]
(111) Lauicyclone A	Croton laui	Leaves	MCF-7	MTT	IC50 = 36.7 µM	Li et al. [43]
(112) Lauicyclone B	Croton laui	Leaves	MCF-7	MTT	IC50 = 24.6 µM	Li et al. [43]
(113) Lauicyclone D	Croton laui	Leaves	MCF-7	MTT	IC50 = 38.8 µM	Li et al. [43]
(114) Lauicyclone E	Croton laui	Leaves	MCF-7	MTT	IC50 = 49.3 µM	Li et al. [43]

MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. MTS: colorimetric assay.

and Figure 10).

3.10. Crotinsulidane

Compound 115 (EBC-219) isolated from the stem of C. insularis was the only representative of the crotinsulidene group tested against breast cancer cells. This compound showed no relevant effect against MCF-7 cells (

Table 10. Cytotoxicity of crotinsulidane from Croton species against breast cancer cell lines.

Compound	Species	Plant Part	Cancer Cell Line	Method	Results	References
(115) EBC-219	Croton insularis	Stem	MCF-7	MTS	IC50 = 80 µM	Maslovskaya et al. [41]

MTS: colorimetric assay.

and Figure 11).

4. Discussion

Although 115 diterpenoids isolated from Croton species were evaluated for their cytotoxic potential against breast cancer cell lines, only 25 showed promising results (IC₅₀ = < 10 µM). The mechanisms of action of compounds 28 (crokokaugenoid A), 60 (kongensin D), 67 (ent-16β,17α-dihydroxykaurane), and 111 (lauicyclone A) have been well reported in the literature. According to Zhu et al. [28], MDA-MB-231 cells were treated with different concentrations (1, 2 and 4 μM) of compound 28 and, after 48 h, a concentration-dependent cell cycle arrest was observed in the G₂/M phase, while the G₀/G₁ and S phases decreased. Furthermore, both early-stage and late-stage apoptotic cells increased in a dose-dependent manner by up to 16.0% (1 μM), 16.9% (2 μM), and 43.1% (4 μM), respectively. These results indicated that compound 28 effectively induced cell cycle arrest and apoptosis in MDA-MB-231 cells, as well as increased intracellular reactive oxygen species (ROS) levels and regulated the STAT3 and FAK signaling pathways [28].

Compound 60 showed promising anti-TNBC (triple-negative breast cancer) potential in in vitro and in vivo studies. According to Fan et al. [24], murine models of TNBC xenograft were developed by subcutaneous injection of MDA-MB-468 cells into female NOD/SCID mice and treated with compound 60 at doses of 5 and 10 mg/kg per day, via intraperitoneal injection. After 33 days, compound 60 was observed to suppress the growth of xenotransplanted TNBC tumors in a dose-dependent manner. Additionally, investigations revealed that the levels of phosphorylated Akt (p-Akt) and its downstream target, phosphorylated mTOR (p-mTOR), decreased significantly with treatment with compound 60 in a dose-dependent manner, while the level of its upstream target, phosphorylated PI3K (p-PI3K), was not changed [24]. Moreover, compound 60 had no influence on the expression of PI3K, Akt, and mTOR, suggesting that it could affect the phosphorylation cascades downstream of p-PI3K [24]. Mechanistic studies in MDA-MB-231 and MDA-MB-468 cells revealed that compound 60 can induce apoptosis, autophagy, G₂/M cell cycle arrest, and inhibit cell migration and invasion. These promising cytotoxic effects of compound 60 may be related to the cleavage of the C8-C9 bond and the presence of the α,β-unsaturated ketone moiety [24].

Similar to compound 60, compound 62 (kongensin A) was also effective against the MDA-MB-231, MDA-MB-468, and MCF-7 cell lines [24]. According to Li et al. [44], compound 62 inhibits RIP3-dependent necroptosis and favors apoptosis in several cancer cell lines. The mechanism involves covalent binding to cysteine 420 of HSP90, which destabilizes the complex formed with the co-chaperone CDC37. On the other hand, Chen et al. [45] reported that low concentrations of compound 62 blocked necroptosis, exerted anti-inflammatory effects on NPCs (nucleus pulposus cells), and inhibited apoptosis. This phenomenon was investigated through RNA-seq analysis, where it was observed that compound 62 significantly increased the expression of TAK1. This increase was crucial for restoring mitochondrial function, as it mitigated oxidative stress and the production of reactive oxygen species (ROS) induced by TBHP (tert-butyl hydroperoxide) in NPCs, culminating in the inhibition of PANoptosis [45].

In a study by Morales et al. [25], it was reported that MCF-7 cells treated with compound 67 at a concentration of 12.5 μg/mL showed a reduction in Bcl-2 and hTERT levels. Furthermore, after 24 h of treatment with compound 67 (12.5 μg/mL), the MCF-7 cell line showed a marked pattern of DNA fragmentation [25]. According to Morales et al. [46], compound 67 dissociates the Ap2α-Rb activator complex from the Bcl-2 gene promoter and induces the translocation of Ap2α from the nucleus to the cell periphery without affecting Rb. This effect contributes to the initiation of apoptosis through the downregulation of Bcl-2 [46]. Regarding the mechanisms of action of compound 111 in MCF-7 cells, it has been reported that the cytotoxic effect may be associated with cellular bio-oxidation pathways and glucose metabolism [43]. In this context, Li et al. [43] reported that compound 111 can influence the expression of HIF-1α, promoting cellular glucose uptake and reducing pyruvate entry into the Krebs cycle.

The cytotoxic activity of compounds isolated from Croton justifies the use of these plants in the traditional medicine of several countries for the treatment of cancer. According to ethnobotanical and ethnopharmacological surveys, the species C. penduliflorus [47], C. lechleri [48], C. draconoides [49], C. urucurana [50,51] C. macrostachyus [52,53,54,55], C. heliotropiifolius [56], and C. gratissimus [57] are widely used for cancer treatment in countries in Africa and South America. However, records regarding the isolation of diterpenes and tests on breast cancer cell lines have not yet been found for these plants. This ethnomedicinal information can guide future studies on the cytotoxic potential of diterpenes from these species used in traditional communities.

Croton is not the only genus in the Euphorbiaceae family that includes species rich in diterpenoids with cytotoxic effects. Several studies have reported that diterpenoids such as pubescenol, helioscopinolide A–B, curcusone B, jatrophalactone, jatrophaketone, jatrophadiketone, jatrocurcasenones A–E, jatrophodiones B–E, curcusecons A–E, curcusones F–J, ent-atisane, myrsinanes, premyrsinanes, jatrophone, and resiniferatoxin have been isolated from the species Euphorbia pubescens [58], Jatropha curcas [59,60,61,62], Jatropha ribifolia [63], Euphorbia connata [64], Euphorbia fischeriana [65], Jatropha gossypiifolia [66], Euphorbia sororia [67], Euphorbia bicolor [68], Euphorbia gedrosiaca [69], and Jatropha spinosa [70]. All of these diterpenoids have also been investigated against breast cancer cell lines, particularly MCF-7 cells. In this context, the Euphorbiaceae family stands out as a source of diterpenoids with potential anti-breast cancer properties.

Although this review has focused only on diterpenoids isolated from Croton species, it is important to highlight that essential oils obtained from C. argyrophyllus [71,72], C. campestris [73], C. doctoris [74], C. heliotropiifolius [75], C. malambo [76], C. matourensis [77], and C. urucurana [78] have also been investigated against the MDA-MB-435 and MCF-7 breast cancer cell lines. Considering that essential oils are rich in monoterpenes and sesquiterpenes, the planning and development of pharmaceutical formulations containing terpenes obtained from these plants are necessary to evaluate their potential in the treatment of cancer patients, especially against breast cancer.

5. Future Perspectives

To date, no randomized clinical trials have been conducted using Croton diterpenoids for the treatment of breast cancer. Most studies are limited to in vitro assays, with considerable gaps related to the possible mechanisms of action of these natural products. Therefore, pharmacokinetic, pharmacodynamic, and toxicokinetic studies of these compounds are of great importance to ensure their use as potential anticancer agents in the future.

Based on in vitro and in vivo studies, bioactive compounds have been shown to have a positive effect on the immune system and its ability to fight cancer cells. In murine models of triple-negative breast cancer (TNBC), for example, natural products can be investigated for their immunotherapeutic activity in the tumor microenvironment (TME) during breast cancer progression [79]. These compounds have been reported can reverse tumor signaling pathways associated with the immune system, restoring its normal function by inhibiting the secretion of TGF-β, PGE2, and IL-10, as well as promoting the secretion of antitumor factors such as IFN-γ, TNF-α, and IL-1β [80]. Taken together, this promising evidence encourages the development of future studies focused on the possibility of modulating the immune response in breast cancer cell lines using diterpenoids from Croton species.

Furthermore, the use of nanotechnology combined with Croton diterpenoids can improve the bioavailability of these molecules, intensifying and targeting their effects against tumor cells. It has been reported that nanoparticles based on compounds such as carbon, dendrimers, lipids, polymers, proteins, secondary metabolites, as well as metallic and mesoporous silica nanoparticles, represent the main classes of nanostructured drug delivery systems that have been explored for breast cancer therapy [81]. According to Sharmila et al. [82], terpene-based nanoformulations offer several advantages in drug delivery, as they improve solubility, bioavailability, and biocompatibility, overcoming the disadvantages of plant-derived terpenoids used in cancer treatment. Among other advantages, nanotechnology allows for the administration of natural products specifically targeted to cancer cells, which directly contributes to safer treatment free from side effects [83]. In this context, the structural modification of natural products, in combination with biosynthetic and computational technologies, will become an important direction for the development of future studies against breast cancer [84].

6. Conclusions

Although 115 diterpenoids were isolated from 15 Croton species and evaluated for their cytotoxic potential, only 25 showed promising results when tested against the MDA-MB-231, MCF-7, and MDA-MB-468 cell lines. Most of the compounds tested belong to the kaurane group, followed by clerodane, tigliane, abietane, pimarane, cembrane, crotofolane, casbane, labdane, and crotinsulidane. The mechanisms of action of the compounds crokokaugenoid A, kongensin A, kongensin D, ent-16β,17α-dihydroxykaurane, and lauicyclone A have been reported. These compounds likely act by inducing apoptosis, autophagy, cell cycle arrest, inhibition of cell migration and invasion, and DNA fragmentation in breast cancer cell lines.