Isocupressic Acid

Isocupressic Acid at a Glance

Isocupressic acid is a labdane diterpene acid — 15-hydroxylabda-8(17),13E-dien-19-oic acid — found in the needles of several conifers at around one to two percent of dry weight. It is the reason cattle that graze pine needles in late pregnancy abort.

That sounds like folklore and is not. Ranchers in the western United States reported the association for most of the twentieth century; the USDA Poisonous Plant Research Laboratory reproduced it experimentally, isolated the compound responsible, measured its content in each implicated species, worked out how it is metabolised, and built a serum assay to diagnose affected animals ^{1,5,6Reference 1Lee ST et al. · 2003AnimalDevelopment of enzyme-linked immunosorbent assays for isocupressic acid and serum metabolites of isocupressic acid — animal modelView study →Reference 5James LF et al. · 1989ReviewPine needle abortion in cattle: a review and report of 1973-1984 research — reviewView study →Reference 6Gardner DR et al. · 1999ReviewPonderosa pine and broom snakeweed: poisonous plants that affect livestock — reviewView study →}. Very few plant molecules have that complete a chain — a named compound, a measured content, a reproducible species-level effect, and a diagnostic marker.

What it does not have is any human data. Nobody has studied isocupressic acid in people, and the question “is pine needle tea safe in pregnancy?” cannot be answered from this literature. What the literature does give is something more useful than a verdict: it says exactly which species carry the compound, at what levels, and what happened to the one species that has been tested.

The Cattle Story, Precisely

The experimental work is unusually specific, so it is worth stating in its own terms rather than in summary.

Late-pregnant cows were fed ground needles by gavage from around day 250 of gestation. Needles from lodgepole pine contained 0.8% isocupressic acid by dry weight and delivered 62–78 mg/kg body weight daily; those cows aborted after 8 and 10 days. Needles and plant material from common juniper ran higher, at 2.0%, delivering 190–245 mg/kg daily; those cows aborted after 3 and 4 days. All retained fetal membranes and showed the classical clinical picture of pine-needle abortion ^{2Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →}.

Content in the other implicated species has been measured on the same basis: ponderosa pine needles from Oregon at 1.70%, and Monterey cypress from New Zealand at 0.89–1.24% — the New Zealand measurement made to test a local anecdotal association, which it supported ^{3Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →}. Cases are still reported where the plants and the cattle overlap, including a recent series from Argentina ^{15Reference 15Martinez A et al. · 2024Case reportPine needle abortions in cattle due to consumption of Pinus ponderosa in Argentina: case reports — case reportView study →}.

Two details do a lot of work here, and both cut against reading this as a general warning about conifers.

The dose is agricultural. These are cows eating kilograms of needles a day for days on end. The exposure is not comparable to a cup of tea, and no threshold below which the effect disappears has been established in any species.

Isocupressic acid causes abortion and almost nothing else. When ponderosa pine tips, rosin gum and dehydroabietic acid were compared head to head in pregnant cattle, the pine tips both aborted and poisoned; rosin gum and dehydroabietic acid poisoned without aborting — anorexia, rumen acidosis, dyspnoea, progressive paresis, nephrosis, myonecrosis — while isocupressic acid at abortifacient doses caused no other toxicosis ^{4Reference 4Stegelmeier BL et al. · 1996AnimalThe toxic and abortifacient effects of ponderosa pine — animal modelView study →}. The abortion belongs to the labdane; the general toxicosis belongs to the abietane resin acids. They are separate hazards in the same tree, and conflating them makes both harder to understand.

What It's Used For

The mechanistic work is small, consistent, and mostly about steroid production. It also contains one result that runs against the intuition the rest of the story creates.

Abortion in cattle is established, not inferred.Reproduced experimentally in controlled feeding trials across four plant species, with content measured in each ^{2,3,4Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →Reference 4Stegelmeier BL et al. · 1996AnimalThe toxic and abortifacient effects of ponderosa pine — animal modelView study →}.

The mechanism runs through the corpus luteum.Isocupressic acid inhibited progesterone production from bovine luteal cells at every concentration tested, under basal, LH-stimulated and cAMP-stimulated conditions — pointing to a post-cAMP step ^{7Reference 7Wu LS et al. · 2002In vitroIsocupressic acid blocks progesterone production from bovine luteal cells — in vitroView study →}, with a parallel suppression of steroidogenesis in a Leydig cell line ^{8Reference 8Tsui KH et al. · 2012In vitroMolecular mechanism of isocupressic acid supresses MA-10 cell steroidogenesis — in vitroView study →}.

It is not a general embryotoxin.Added to bovine in-vitro maturation and culture media, it did not impair oocyte maturation or preimplantation embryo development; it modestly enhanced embryo development, and blastocysts cultured with it transferred to recipient heifers produced normal pregnancies and normal calves ^{9Reference 9Wang S et al. · 2004AnimalEffects of the pine needle abortifacient, isocupressic acid, on bovine oocyte maturation and preimplantation embryo development — animal modelView study →}.

It disappears fast and leaves a marker.Rumen and blood convert it within hours to agathic, dihydroagathic and tetrahydroagathic acids — which is why the metabolites, not the parent, are what diagnostic assays look for ^{10,11,12,13Reference 10Lin SJ et al. · 1998In vitroIn vitro biotransformations of isocupressic acid by cow rumen preparations: formation of agathic and dihydroagathic acids — in vitroView study →Reference 11Gardner DR et al. · 1999AnimalPine needle abortion in cattle: metabolism of isocupressic acid — animal modelView study →Reference 12Garrossian M et al. · 2002Preparation of tetrahydroagathic acid: a serum metabolite of isocupressic acid, a cattle abortifacient in ponderosa pineView study →Reference 13Snider DB et al. · 2015AnimalPine needle abortion biomarker detected in bovine fetal fluids — animal modelView study →}.

Evidence by IndicationStrength of support · Beta

The core finding, and the only one at the whole-animal level. Feeding trials in late-gestation cows established the effect for ponderosa pine, lodgepole pine, common juniper and Monterey cypress, with isocupressic acid identified as the primary abortifacient across all four and its content measured in each ^{1,2,3Reference 1Lee ST et al. · 2003AnimalDevelopment of enzyme-linked immunosorbent assays for isocupressic acid and serum metabolites of isocupressic acid — animal modelView study →Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →}.

Abortion follows within days at agricultural intakes, with retained fetal membranes as a consistent feature ^{2Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →}.

Importantly, the co-occurring vasoactive lipids of ponderosa pine — myristate and laurate esters of long-chain diols, once proposed as the abortifacient — were shown not to be required: lodgepole material caused abortion at similar rates while Monterey cypress contained none of them at all ^{2Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →}.

Metabolism differs between cattle habituated to eating needles and naive animals, which is one reason field incidence varies ^{16Reference 16Welch KD et al. · 2012AnimalA comparison of the metabolism of the abortifacient compounds from Ponderosa pine needles in conditioned versus naive cattle — animal modelView study →}.

Gap: the entire whole-animal record is cattle, at grazing-scale doses. No other species has been tested at any dose, and the literature is a veterinary toxicology one throughout ^{17Reference 17Coy D et al. · 2024ReviewSome phytotoxins causing reproductive alterations in ruminants — reviewView study →}.

Mechanisms

Target / pathway	Effect	Relevant to
Bovine luteal progesterone synthesis	inhibited at all tested concentrations, including under direct cAMP stimulation — a post-cAMP block	abortifacient mechanism
Leydig-cell steroidogenesis (MA-10)	suppressed, indicating a general steroidogenic rather than luteal-specific action	abortifacient mechanism
Rumen and hepatic metabolism	rapid conversion to agathic → dihydroagathic → tetrahydroagathic acid	pharmacokineticsdiagnosis
Plant root elongation	strongly inhibited — allelopathic defence	ecology
Bovine oocyte maturation and preimplantation embryo	not impaired; embryo development enhanced in culture	what the molecule does not do

Pharmacokinetics

Characterised in cattle, and nowhere else. Isocupressic acid is rapidly and extensively metabolised — rumen preparations convert it in vitro to agathic acid and dihydroagathic acid ^{10Reference 10Lin SJ et al. · 1998In vitroIn vitro biotransformations of isocupressic acid by cow rumen preparations: formation of agathic and dihydroagathic acids — in vitroView study →}, and in the intact animal the sequence continues to tetrahydroagathic acid, which is what actually circulates ^{11,12Reference 11Gardner DR et al. · 1999AnimalPine needle abortion in cattle: metabolism of isocupressic acid — animal modelView study →Reference 12Garrossian M et al. · 2002Preparation of tetrahydroagathic acid: a serum metabolite of isocupressic acid, a cattle abortifacient in ponderosa pineView study →}. The parent compound is largely gone by the time an animal is sampled, so the diagnostic assays were built against the metabolites: competitive-inhibition ELISAs cross-reacting with agathic, dihydroagathic and tetrahydroagathic acids, with the isocupressic-acid-specific assay reaching a limit of detection of 44.1 pg ^{1Reference 1Lee ST et al. · 2003AnimalDevelopment of enzyme-linked immunosorbent assays for isocupressic acid and serum metabolites of isocupressic acid — animal modelView study →}. The same marker has since been detected in bovine fetal fluids, allowing a diagnosis to be made from the aborted fetus rather than the cow ^{13Reference 13Snider DB et al. · 2015AnimalPine needle abortion biomarker detected in bovine fetal fluids — animal modelView study →}. Cattle conditioned to eating pine needles metabolise the compound differently from naive animals ^{16Reference 16Welch KD et al. · 2012AnimalA comparison of the metabolism of the abortifacient compounds from Ponderosa pine needles in conditioned versus naive cattle — animal modelView study →}.

No absorption, distribution or elimination data exist for any non-ruminant species, and none for humans.

Clinical Trials

None, and none should be expected — this is a poisonous-plant research programme, not a drug programme. The entire animal literature is livestock toxicology, and the entire human literature is empty.

Completed	Planned	Terminated	Preclinical
None in humans	—	—	Cattle feeding trials, bovine luteal and Leydig cell work, embryo culture, rumen metabolism

Last checked: September 2026.

Isolate vs. Plant Studies

Both, and they agree — which is rare enough to be worth saying. The whole plant was tested first: ground needles fed to pregnant cattle, with abortion as the endpoint and content measured in the material actually fed ^{2,3Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →}. The isolated molecule was then tested in cells, where it produced a mechanism consistent with the whole-plant result ^{7,8Reference 7Wu LS et al. · 2002In vitroIsocupressic acid blocks progesterone production from bovine luteal cells — in vitroView study →Reference 8Tsui KH et al. · 2012In vitroMolecular mechanism of isocupressic acid supresses MA-10 cell steroidogenesis — in vitroView study →}. And a negative control within the plant was run too: rosin gum and dehydroabietic acid, fed to the same kind of animal, poisoned without aborting ^{4Reference 4Stegelmeier BL et al. · 1996AnimalThe toxic and abortifacient effects of ponderosa pine — animal modelView study →}, which is what isolates the labdane as the abortifacient rather than the resin generally.

The transferability caveat is about species, not about isolate-versus-plant. Everything at the organism level is cattle. Sheep, horses and humans have not been tested, and the ruminant metabolism that dominates the pharmacokinetics does not exist in a person.

Its Role in Plants

Isocupressic acid is a labdane, formed from geranylgeranyl diphosphate by a different branch of conifer diterpene metabolism than the abietane resin acids of the oleoresin — which is why it concentrates in needles rather than in pitch, and why the two hazards separate so cleanly by plant part.

Its function appears to be allelopathic. In Pinus pinea, bio-guided fractionation identified it as the needle extract’s principal phytotoxin, strongly inhibiting root growth in competing weeds ^{14Reference 14Hlaili H et al. · 2025In vitroMetabolite screening from Pinus pinea needles reveals (+)-isocupressic acid as a key phytotoxin for weed management — in vitroView study →}. Pine needle litter is famously inhibitory to understorey germination, and this is one of the molecules behind it. That it also interferes with mammalian steroidogenesis is incidental — a defence compound with an off-target effect in an animal that eats it.

Prevalence in Nature

Isocupressic acid is documented in a specific, short list of conifers, and the list matters more than the general family:

Species	Part	Content (% dry weight)
Common juniper (Juniperus communis)	needles / plant material	~2.0% ^{2Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →}
Ponderosa pine (Pinus ponderosa)	needles	~1.70% (Oregon material) ^{3Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →}
Monterey cypress (Cupressus macrocarpa)	foliage	0.89–1.24% (New Zealand material) ^{3Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →}
Lodgepole pine (Pinus contorta)	needles	~0.8% ^{2Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →}
Stone pine (Pinus pinea)	needles	present; isolated as the principal phytotoxin, not quantified as % dry weight ^{14Reference 14Hlaili H et al. · 2025In vitroMetabolite screening from Pinus pinea needles reveals (+)-isocupressic acid as a key phytotoxin for weed management — in vitroView study →}
Taiwan cypress (Juniperus formosana)	root	present; the source used for the luteal-cell work ^{7Reference 7Wu LS et al. · 2002In vitroIsocupressic acid blocks progesterone production from bovine luteal cells — in vitroView study →}

The compound is named as an isomer of cupressic acid, first characterised from Cupressus — which is why a molecule best known from pines carries a cypress name.

What is not known is as important as what is. The genus Pinus has not been systematically surveyed for isocupressic acid, and the species most commonly used for needle tea — Scots pine (P. sylvestris) and eastern white pine (P. strobus) — do not appear in this literature either as positives or as negatives. An absence of reports is not a measurement of zero. Content also varies with season, tissue and population, as it does for every conifer diterpene.

Discovery & Synthesis

The abortion came first and the chemistry followed, over about seventy years. Field reports of cattle aborting after grazing ponderosa pine were recorded from early in the twentieth century; the USDA Poisonous Plant Research Laboratory reproduced the abortions experimentally through the 1970s and early 1980s, and a 1989 review of that decade of work concluded that the abortifacient principle varied markedly between years and collection sites — a strong hint that a specific, variable compound was responsible rather than the needles as such ^{5Reference 5James LF et al. · 1989ReviewPine needle abortion in cattle: a review and report of 1973-1984 research — reviewView study →}. Isocupressic acid was identified as that compound in the early 1990s, and by the mid-1990s it was being quantified across species and tested as a purified isolate ^{3,4,6Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →Reference 4Stegelmeier BL et al. · 1996AnimalThe toxic and abortifacient effects of ponderosa pine — animal modelView study →Reference 6Gardner DR et al. · 1999ReviewPonderosa pine and broom snakeweed: poisonous plants that affect livestock — reviewView study →}.

There is no manufacturing route and no reason for one. The compound is isolated from plant material for research use; the only synthetic chemistry associated with it is the preparation of its metabolite tetrahydroagathic acid as an analytical standard for the diagnostic assays ^{12Reference 12Garrossian M et al. · 2002Preparation of tetrahydroagathic acid: a serum metabolite of isocupressic acid, a cattle abortifacient in ponderosa pineView study →}, and microbial transformation studies used to generate related structures.

Patents: not yet researched.

Toxicity & Safety

The toxicology here is precise about cattle and silent about everything else. Both halves of that need saying.

Safety at a Glance

Moderate toxicity

A proven abortifacient in cattle at grazing-scale intakes, in the last trimester, from four documented plant species ^{2,3Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →}.
No human data of any kind. No exposure study, no case report, no pharmacokinetics. The absence is not reassurance; it is an absence.
Species and part are what determine exposure. The compound is in needles and foliage of specific conifers, not in resin or pitch — and the pine species used for needle tea have not been assayed either way.
It is not a general poison. At abortifacient doses in cattle it produced no other toxicosis, and it did not harm oocytes or early embryos in culture ^{4,9Reference 4Stegelmeier BL et al. · 1996AnimalThe toxic and abortifacient effects of ponderosa pine — animal modelView study →Reference 9Wang S et al. · 2004AnimalEffects of the pine needle abortifacient, isocupressic acid, on bovine oocyte maturation and preimplantation embryo development — animal modelView study →}.

Full Safety & Interactions Detail

What is established. Late-gestation abortion in cattle, reproduced experimentally, with the compound identified, its content in each source plant measured, its metabolism mapped and a diagnostic assay validated ^{1,2,3,12,13Reference 1Lee ST et al. · 2003AnimalDevelopment of enzyme-linked immunosorbent assays for isocupressic acid and serum metabolites of isocupressic acid — animal modelView study →Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →Reference 3Parton K et al. · 1996AnimalIsocupressic acid, an abortifacient component of Cupressus macrocarpa — animal modelView study →Reference 12Garrossian M et al. · 2002Preparation of tetrahydroagathic acid: a serum metabolite of isocupressic acid, a cattle abortifacient in ponderosa pineView study →Reference 13Snider DB et al. · 2015AnimalPine needle abortion biomarker detected in bovine fetal fluids — animal modelView study →}. Clinical signs in the cow are dominated by the abortion itself and retained fetal membranes; at abortifacient doses no additional toxicosis was seen ^{4Reference 4Stegelmeier BL et al. · 1996AnimalThe toxic and abortifacient effects of ponderosa pine — animal modelView study →}.

What is not established, and matters. There is no human exposure literature. There is no study in any non-ruminant. There is no threshold dose in any species. The proposed mechanism — suppression of luteal progesterone production, plausibly reducing uterine support in late gestation — is supported by cell work ^{7,8Reference 7Wu LS et al. · 2002In vitroIsocupressic acid blocks progesterone production from bovine luteal cells — in vitroView study →Reference 8Tsui KH et al. · 2012In vitroMolecular mechanism of isocupressic acid supresses MA-10 cell steroidogenesis — in vitroView study →} but has not been closed in vivo, and human pregnancy does not depend on the corpus luteum in the third trimester the way bovine pregnancy does. That difference is a reason not to extrapolate in either direction, not a reason to assume safety.

The practical question. Pine needle tea is a real traditional preparation, and this is the compound behind the question of whether it is appropriate in pregnancy. The honest answer from this literature is a sourcing one: the species with documented isocupressic acid content are ponderosa pine, lodgepole pine, common juniper, Monterey cypress and stone pine, and juniper and ponderosa carry the most. Those are worth avoiding in pregnancy on the evidence available. The species usually sold for needle tea have not been assayed, which means the question is open rather than answered, and an open question in pregnancy is normally decided conservatively.

Interactions. None characterised. No CYP, transporter or drug-interaction work exists for this molecule.

Other reproductive findings. In the one direct test, isocupressic acid did not impair bovine oocyte maturation or preimplantation embryo development, and embryos cultured with it went on to normal pregnancies and normal calves ^{9Reference 9Wang S et al. · 2004AnimalEffects of the pine needle abortifacient, isocupressic acid, on bovine oocyte maturation and preimplantation embryo development — animal modelView study →}. The reproductive hazard documented for this compound is specifically late-gestation and maternal, not embryotoxic.

Dosage

There is no dose, and there should not be one. Isocupressic acid is a livestock-poisoning agent. The figures below are the feeding-trial exposures and plant contents that define the hazard.

Context	Form	Figure reported
Lodgepole pine feeding trial	4.5–5.5 kg/day ground dry needles, from gestation day 250	62–78 mg ICA/kg body weight/day → abortion at 8 and 10 days ^{2Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →}
Common juniper feeding trial	same protocol	190–245 mg ICA/kg body weight/day → abortion at 3 and 4 days ^{2Reference 2Gardner DR et al. · 1998AnimalAbortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal modelView study →}
Bovine luteal cell culture	isolated compound	1–1000 ng/mL, progesterone inhibited across the whole range ^{7Reference 7Wu LS et al. · 2002In vitroIsocupressic acid blocks progesterone production from bovine luteal cells — in vitroView study →}
Bovine embryo culture	isolated compound	1.3 and 2.6 µg/mL, no adverse effect on maturation or development ^{9Reference 9Wang S et al. · 2004AnimalEffects of the pine needle abortifacient, isocupressic acid, on bovine oocyte maturation and preimplantation embryo development — animal modelView study →}

These are animal research exposures, not doses for anyone to take, and no human intake of isocupressic acid has been characterised.

References

Lee ST, Gardner DR, Garrosian M, et al. (2003). Development of enzyme-linked immunosorbent assays for isocupressic acid and serum metabolites of isocupressic acid — animal model. J Agric Food Chem. https://pubmed.ncbi.nlm.nih.gov/12744647/
Gardner DR, Panter KE, James LF, et al. (1998). Abortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle — animal model. Vet Hum Toxicol. https://pubmed.ncbi.nlm.nih.gov/9778758/
Parton K, Gardner D, Williamson NB (1996). Isocupressic acid, an abortifacient component of Cupressus macrocarpa — animal model. N Z Vet J. https://pubmed.ncbi.nlm.nih.gov/16031906/
Stegelmeier BL, Gardner DR, James LF, et al. (1996). The toxic and abortifacient effects of ponderosa pine — animal model. Vet Pathol. https://pubmed.ncbi.nlm.nih.gov/8826003/
James LF, Short RE, Panter KE, et al. (1989). Pine needle abortion in cattle: a review and report of 1973-1984 research — review. Cornell Vet. https://pubmed.ncbi.nlm.nih.gov/2643502/
Gardner DR, James LF, Panter KE, et al. (1999). Ponderosa pine and broom snakeweed: poisonous plants that affect livestock — review. J Nat Toxins. https://pubmed.ncbi.nlm.nih.gov/10091125/
Wu LS, Chen JC, Sheu SY, et al. (2002). Isocupressic acid blocks progesterone production from bovine luteal cells — in vitro. Am J Chin Med. https://pubmed.ncbi.nlm.nih.gov/12568280/
Tsui KH, Wang JY, Wu LS, et al. (2012). Molecular mechanism of isocupressic acid supresses MA-10 cell steroidogenesis — in vitro. Evid Based Complement Alternat Med. https://pubmed.ncbi.nlm.nih.gov/22666287/
Wang S, Panter KE, Gardner DR, et al. (2004). Effects of the pine needle abortifacient, isocupressic acid, on bovine oocyte maturation and preimplantation embryo development — animal model. Anim Reprod Sci. https://pubmed.ncbi.nlm.nih.gov/14998650/
Lin SJ, Short RE, Ford SP, et al. (1998). In vitro biotransformations of isocupressic acid by cow rumen preparations: formation of agathic and dihydroagathic acids — in vitro. J Nat Prod. https://pubmed.ncbi.nlm.nih.gov/9461652/
Gardner DR, Panter KE, James LF (1999). Pine needle abortion in cattle: metabolism of isocupressic acid — animal model. J Agric Food Chem. https://pubmed.ncbi.nlm.nih.gov/10552582/
Garrossian M, Gardner DR, Panter KE, et al. (2002). Preparation of tetrahydroagathic acid: a serum metabolite of isocupressic acid, a cattle abortifacient in ponderosa pine. J Agric Food Chem. https://pubmed.ncbi.nlm.nih.gov/11929277/
Snider DB, Gardner DR, Janke BH, et al. (2015). Pine needle abortion biomarker detected in bovine fetal fluids — animal model. J Vet Diagn Invest. https://pubmed.ncbi.nlm.nih.gov/25428187/
Hlaili H, Zorrilla JG, Salvatore MM, et al. (2025). Metabolite screening from Pinus pinea needles reveals (+)-isocupressic acid as a key phytotoxin for weed management — in vitro. Phytochem Anal. https://pubmed.ncbi.nlm.nih.gov/40448335/
Martinez A, Apostolo R, Herrera R, et al. (2024). Pine needle abortions in cattle due to consumption of Pinus ponderosa in Argentina: case reports — case report. Toxicon. https://pubmed.ncbi.nlm.nih.gov/38614243/
Welch KD, Gardner DR, Pfister JA, et al. (2012). A comparison of the metabolism of the abortifacient compounds from Ponderosa pine needles in conditioned versus naive cattle — animal model. J Anim Sci. https://pubmed.ncbi.nlm.nih.gov/22696617/
Coy D, Cruz-Carrillo A, Lizarazo-Cely S (2024). Some phytotoxins causing reproductive alterations in ruminants — review. Toxicon. https://pubmed.ncbi.nlm.nih.gov/38795851/