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HORTSCIENCE 60(1):17–22. 2025. https://doi.org/10.21273/HORTSCI18240-24
Apigenin Accumulation in Matricaria
chamomilla and Petroselinum crispum
Produced in a Vertical Hydroponic
System
Rebekah C.I. Maynard
Department of Horticulture, University of Georgia, 1111 Plant Sciences
Building, Athens, GA 30602, USA
Samuel O. Ogundipe
Department of Food Science & Technology, University of Georgia, Food
Science Building, Athens, GA 30602, USA
Rhuanito Soranz Ferrarezi
Department of Horticulture, University of Georgia, 1111 Plant Sciences
Building, Athens, GA 30602, USA
Joon Hyuk Suh
Department of Food Science & Technology, University of Georgia, Food
Science Building, Athens, GA 30602, USA
Leonardo Lombardini
Department of Horticulture, University of Georgia, 1111 Plant Sciences
Building, Athens, GA 30602, USA
Keywords. anticancer, biopharmaceutical, controlled environment
Abstract. Apigenin, an anticancer secondary metabolite, is produced in selected or-
gans of a few plant taxa, including chamomile (Matricaria chamomilla)flowers and
parsley (Petroselinum crispum) leaves. In this study, two cultivars of chamomile (Bodegold
and Zloty Lan) and three cultivars of parsley (Darki, Giant of Italy, and Wega) were in-
cluded in an indoor vertical farm trial to determine apigenin accumulation and biomass
production. Vertical farming was selected for its ability to produce a quality crop with a
tightly controlled growing environment. The plants were started from seed in a growth
chamber and transferred to the vertical farm when they reached two sets of true leaves. The
plants were maintained solely under light-emitting diodes with daily light integrals of 19 and
17 mol·m
22
·d
21
for parsley and chamomile, respectively. The photoperiod was set to 16 hours
for both species to induce flowering in the chamomile. After 15 weeks, mature parsley leaves
and unopened chamomile inflorescences were harvested for analysis. All plants matured quickly
during the growing period; however, only 63% of the ‘Zloty Lan’chamomile plants produced
flowers. At harvest, the total dry mass of each plant was also recorded. The Giant of Italy
cultivar produced significantly more usable biomass compared with that of any other culti-
var of parsley or chamomile, with 49.3 g usable tissue per plant. Apigenin was extracted
from lyophilized samples and quantified using high-performance liquid chromatography–
ultraviolet detection. The results showed that total apigenin accumulation was significantly
higher in the ‘Bodegold’chamomile compared to any parsley cultivar, with 0.70 mg·g
21
dried tissue. Additionally, ‘Bodegold’generated significantly more usable biomass, suggest-
ing that this cultivar shows potential for producing apigenin in a controlled environment.
Plants have long been used for their medici-
nal purposes, and natural products isolated
from many genera still contribute to modern
drug development (Jamshidi-Kia et al. 2018).
Through domestication, cultivation, and breed-
ing, medicinal plants have an increased growth
rate, higher concentration of desirable com-
pounds, and greater biomass of the target tis-
sues (Faehnrich et al. 2021). The medicinal
benefits of plants are the result of secondary
metabolite production and accumulation of
alkaloids, phenolic compounds, and terpe-
noids (Kabera et al. 2014). For example, the
alkaloid colchicine is an antitumor agent
derived from autumn crocus (Colchicum
autumnale), the furocoumarin khellin is a
bronchodilator isolated from toothpick weed
(Ammi visnaga), and the glycoside acetyldi-
goxin is a cardiotonic derived from wooly
foxglove (Digitalis lantana) (Fabricant and
Farnsworth 2001).
Phenolic compounds are one of the most
prevalent secondary metabolites and have
several functions in plants such as contribut-
ing to flavor and color and providing defense
against biotic and abiotic stressors (Righini
et al. 2019; Soto-Vaca et al. 2012). Flavonoids
are the largest group of phenolics, with at least
2000 compounds found widely in plants (Soto-
Vaca et al. 2012). Apigenin, an important fla-
vonoid, is produced in several fruits, veget a-
bles, and herbs, including celery (Apium
graveolens) (Yan et al. 2014), chamomile
(Matricaria chamomilla) (Letchamo 1996),
citrus (Citrus spp.) (Abad-Garc
ıa et al. 2014),
oregano (Origanum spp.) (Mueller et al. 2008),
and parsley (Petroselinum crispum) (Poureini
et al. 2022). Apigenin is one of the most cyto-
toxically active flavones against many cancers,
including bladder (Zhu et al. 2013), breast
(Pham et al. 2021), cervical (Chen et al.
2022), colorectal (Cheng et al. 2021), and
prostate (Costea et al. 2020) cancers. It has
also been approved by the Food and Drug
Administration for use as combination can-
cer therapy to reduce resistance to traditional
cancer treatments (Nozhat et al. 2021). Other
medicinal applications of apigenin include anti-
bacterial (Kim et al. 2020), antifungal (Singh
et al. 2014), anti-inflammatory (Wang et al.
2014), and antioxidant properties (Tian et al.
2021). Beyond prescriptive use, the dietary in-
take of apigenin is considered nutritionally safe,
with no signs of toxicity up to 5 g·kg
1
in
mice (Nozhat et al. 2021).
Apigenin accumulation differs across plant
tissues. For example, in physiologically mature
celery, younger leaves have the lowest concen-
tration of apigenin, with concentrations increas-
ing in the more developed leaves (Yan et al.
2014). Additionally, apigenin accumulation dif-
fers in the flowers, leaves, petioles, and seeds
of celery, with the greatest concentration occur-
ring in the leaves (Yan et al. 2014). Although
apigenin can be produced in different plant or-
gans, it is typically isolated from the leaves of
parsley (Poureini et al. 2022) and oregano
(Origanum spp.) (Mueller et al. 2008). How-
ever, in chamomile, apigenin accumulates
primarilyintheflowers, where the highest
concentration occurs in the newly opened
buds, with apigenin levels steadily declining
as the flower head matures (Letchamo 1996).
Although apigenin can be chemically syn-
thesized, the process requires four-step, multi-
day synthesis with a low (55%) yield (Wang
et al. 2015). Because of its low natural abun-
dance, apigenin is costly, thus making it a
desirable target for enhanced production as a
biopharmaceutical (Wang et al. 2018). Other
research increased apigenin production in
Astragalus trigonus through agrobacterium-
mediated transformation with the Chalcone
isomerase A (chiA) gene from petunia (Petunia
hybrida). Production increased from 0.95 mg·g
1
in the control cells to 19.81 mg·g
1
in the
transformed cells (Elarabi et al. 2021).
Although genetic transformation is a viable
method for increasing apigenin production,
many consumers and markets are resistant to
accepting products derived from transgenic
food crops (Teferra 2021).
An alternative method of increasing pro-
ductivity of apigenin is production in con-
trolled environments, namely, indoor vertical
farms. Through their unconventional use of
space, vertical farms can yield greater bio-
mass per acre compared with that of green-
houses or field production and can optimize
HORTSCIENCE VOL. 60(1) JANUARY 2025 17
growth through their tightly controlled growth
conditions. Although advancements in lighting,
irrigation, and automation allow for more effi-
cient production of crops compared to con-
ventional agriculture, energy usage is still a
common concern for indoor systems (Folta
2019). Additionally, the high cost of starting
a new operation caused more than half of
controlled environment farms to be unprofit-
able in 2017 (O’Sullivan et al. 2019). There-
fore, selecting a high-value biopharmaceutical
crop may be necessary to make vertical
farming more cost-effective (Chen and Yeh
2018). Chamomile and parsley, which natu-
rally produce apigenin, are both suitable crops
for an indoor vertical farm because they have a
short production time and compact structure.
We hypothesized that chamomile and parsley
grown in an indoor vertical farm will biosyn-
thesize apigenin in harvestable quantities. The
aim of this research was to determine bio-
mass production and apigenin accumulation
in selected cultivars of chamomile and parsley
as potential biopharmaceutical crops for in-
door vertical farm production.
Materials and Methods
Crop production. Two cultivars of chamo-
mile (Matricaria chamomilla L.), Bodegold
and Zloty Lan (Jelitto Perennial Seeds, Louis-
ville, KY, USA), and three cultivars of pars-
ley (Petroselinum crispum Mill. Nyman ex
A.W. Hill.), Darki, Giant of Italy, and Wega
(Johnny’s Selected Seeds, Winslow, ME, USA),
were selected for a trial in a hydroponic indoor
vertical farm located at the University of Georgia
(College of Agricultural and Environmental
Sciences, Department of Horticulture, CEA
Crop Physiology and Production Laboratory) in
Athens, GA, USA, in Jun 2023. Sixteen seeds
of each cultivar were directly sown onto 3.5- ×
5.5-cm plugs of soilless substrate (Preforma;
Jiffy Growing Solutions, Lorain, OH, USA)
and germinated in a growth chamber. The light-
emitting diode (LED) light intensity was set to
250 mmol·m
2
·s
1
for a 16-h photoperiod with
setpoint values of 25 C, 70% humidity, and
800 mg·L
1
CO
2
. The medium was kept con-
sistently moist through subirrigation. The seed-
lings were ready to transplant 3 weeks after
sowing for chamomile and 5 weeks after sow-
ing for parsley. When two sets of true leaves
appeared, the seedlings were transferred to a
deep-water culture system and placed in net
pots spaced evenly on foam rafts in square
60- × 60- × 10-cm containers.
The vertical farm was designed with
two 1.2- × 0.6- × 2.0-m sections separating
the chamomile and parsley trials. Both sec-
tions were subdivided into four vertically
stacked shelves with two deep-water culture
containers per shelf (Fig. 1). For parsley,
each hydroponic container held a single repli-
cate of the three trialed cultivars, which were
uniformly spaced and randomized in their
placement. Similarly, each chamomile hydro-
ponic container held two uniformly spaced
plants (one of each cultivar). The plants were
grown under an array of three LEDs (RAY
Physiospec Spectrum; Fluence, Austin, TX,
USA) with spectral output of 360 to 780 nm
and 30.5-cm spacing between the media sur-
face and the light source. Based on the rec-
ommended light intensities, the chamomile
and parsley were grown with daily light in-
tegrals of 17 and 19 mol·m
2
·d
1
, respec-
tively (Litvin-Zabal 2019; Otto et al. 2017).
Because chamomile is a long-day flowering
species, both herbs were grown under a photo-
period of 16 h to induce flowering (Otto et al.
2017). Vertical reflectors were installed on both
sides of the shelves to help distribute light
across the canopy. The daytime and nighttime
temperatures were set to 24 and 20 C, respec-
tively, with 800 mg·L
1
of supplemental CO
2
during the day, and a humidity range of 50% to
75%. Air was circulated around the plant can-
opy through convection tubing at a rate of 1.2
m·s
1
with two blower fans per shelf (SEA-
FLO, South Bend, IN, USA).
The net pots were held by a foam raft that
allowed the plant roots to be continuously
submerged in a fertilizer solution. The fertilizer
solution was oxygenated with an air pump and
air stone (Fig. 2), and it was adjusted biweekly
with a stock solution of 16N–1.8P–14.3K
(Jack’s Hydro Feed; JR Peters, Inc. Allentown,
PA, USA). Because the seedlings were not fer-
tilized in the growth chamber, the electrical
conductivity was gradually increased from 0.75
to 1.5 dS·m
1
over a period of 4 weeks in the
vertical farm to prevent shock. The pH was ad-
justed with KOH or H
3
PO
4
to maintain a range
of6.0to6.5,andCaCO
3
was added to each
container to buffer the solution.
Harvest. Based on known apigenin accu-
mulation, the leaves of parsley and unopened
inflorescences of chamomile were considered
the usable tissues. When the chamomile plants
began flowering, unopened (i.e., before dehiscence
Fig. 1. Schematic of the vertical hydroponic system divided into two 1.2- × 0.6- × 2.0 m sections to
separate the parsley and chamomile trials. Blower fans forced air through convection tubing above
the plant canopy to prevent humid pockets. The lighting was supplied by light-emitting diodes
(LEDs) with vertical reflectors to distribute the light. The hydroponic containers held one plant
from each cultivar (three for the parsley and two for the chamomile).
Fig. 2. Schematic of the deep-water culture hydroponic containers where seedlings and media were
held in net pots and spaced on a floating foam raft. The roots were submerged in an aerated nutrient
solution.
Received for publication 3 Oct 2024. Accepted
for publication 18 Oct 2024.
Published online 3 Dec 2024.
We thank Jiffy Products International (Freeman
Agnew) for donating the substrate and Agrify
(Micah Gilbert) for donating the LED lights used
in this study. We also thank Matthew Housley for
helping to construct the vertical farm and Z€
oe
Prince for assisting with crop production.
R.C.I.M. is the corresponding author. E-mail: rebekah.
maynard@uga.edu.
This is an open access article distributed under
the CC BY-NC license (https://creativecommons.
org/licenses/by-nc/4.0/).
18 HORTSCIENCE VOL. 60(1) JANUARY 2025
of the disc florets) buds were harvested from in-
dividual plants twice per week. The flower
buds were collected in screw-top tubes (Falcon,
Corning Inc., Corning, NY, USA) and im-
mediately placed in liquid nitrogen. Then,
the samples were transferred to a lyophilizer
(Labconco; Marshall Scientific, Hampton,
NH, USA) and dried at 84 C and 0.133 mbar
for 24 h. When the samples were fully desic-
cated, they were stored in the dark until the
chemical analysis was performed. At 14 weeks
after transplant, samples of the fully expanded
parsley leaves were harvested from each plant
and lyophilized as described. The vegetative
tissue of the chamomile plants and the remain-
ing leaves of the parsley plants were separated
and dried at 80 C for 48 h in a forced air oven
(Shel Lab; Stellar Scientific, Baltimore, MD,
USA). After the drying period, the dry weight
of the isolates was recorded.
The combined dried mass of the leaves
and stems was calculated as the total biomass
production for parsley. The combined dry
mass of the inflorescences, leaves, and stems
was calculated as the total biomass for chamo-
mile. RStudio (version 2023.12.01369) was
used for the data analysis.
Sample preparation. The stock solution of
apigenin was prepared at a concentration of 1
mg·mL
1
by dissolving the apigenin standard
(95% purity) in high-performance liquid chro-
matography (HPLC) grade methanol/DMSO
(90/10, v/v) (Sigma-Aldrich, St. Louis, MO,
USA). The working standard solutions (e.g.,
calibration standards) were prepared daily
by diluting the stock solution with methanol
before use. The freeze-dried tissue samples
were pulverized using a mortar and pestle.
Powdered samples (100 mg for parsley and
50 mg for chamomile) were placed in 2-mL
plastic tubes and mixed with 1 mL of 50%
methanol. The samples were vortexed for 5 min
and centrifuged at 13,500 gfor 10 min. The
supernatants were collected, passed through
0.2-mm membrane filters, and injected into
the HPLC system.
High-performance liquid chromatography
analysis. A chemical analysis was performed
using HPLC (Shimadzu Nexera; Shimadzu
Corp., Tokyo, Japan) equipped with a photo-
diode array detector. Apigenin was separated
on a 4.6- × 150-mm analytical column with a
particle size of 5 mm equipped with a guard
column (ZORBAX Eclipse XDB-C18; Agi-
lent Technologies, Santa Clara, CA, USA).
The column temperature was set to 40 C.
The mobile phase was composed of water/
acetonitrile (65/35, v/v, %) containing 0.1%
formic acid (Oakwood Products Inc., Estill,
SC, USA). The flow rate was 1 mL·min
1
with
an injection volume of 10 mL. After chromato-
graphic separation, apigenin was detected at a
ultraviolet wavelength of 336 nm and identified
by comparing the retention times and ultraviolet
spectra with the apigenin standard. Apigenin
was quantified using calibration curves. Lab-
Solutions software (version 5.124) was used for
the HPLC data interpretation and analysis.
Results
Biomass production. Because apigenin ac-
cumulates in the highest concentrations in the
leaves of parsley (Poureini et al. 2022) and
the flowers of chamomile (Letchamo 1996),
these were considered the usable tissues for
biosynthesis of apigenin. The Bodegold chamo-
mile cultivar generated 18.5 ± 20.8 g of flowers
per plant, accounting for 9% of the total bio-
mass (Table 1 and Fig. 3). The large standard
deviation for ‘Bodegold’was observed because
the flowering of three plants was much more
prolific than that of the other five plants. The
Zloty Lan cultivar produced 4.3 ± 4.8 g of
flowers per plant, accounting for 5% of the total
biomass. Again, the large deviation was attrib-
utable to two ‘Zloty Lan’plants that did not
produce flowers. A ttest indicated that there
was no statistically significant difference in the
biomass of flowers of the two cultivars.
Regarding parsley, the Darki, Giant of Italy,
and Wega cultivars produced 21.4 ± 5.1 g,
49.3 ± 15.4 g, and 32.8 ± 11.4 g of leaf tis-
sue per plant, representing 73%, 59%, and
70% of the total plant biomass, respectively.
Although the Darki parsley cultivar had the
highest percentage of usable biomass rela-
tive to total biomass production, the Giant of
Italy cultivar was the most productive overall.
An analysis of variance (ANOVA) for parsley
showed that the dried biomass of the leaves
was significantly different among the cultivars
[F(2) 512; P50.0003]. Tukey’s honestly
significant difference test indicated that t he
Giant of Italy cultivar generated signifi-
cantly more usable biomass than that of culti-
vars Darki or Wega (Table 1 and Fig. 4).
Compared with chamomile, all parsley culti-
vars produced more usable biomass, which
was expected because the leaves of parsley ac-
count for most of the plant biomass. Because
apigenin accumulates in the chamomile flow-
ers, none of the vegetative tissue is used for
extraction.
HPLC method evaluation. Figure 5 shows
the chromatograms of apigenin in a standard
solution and a sample. Apigenin was clearly
separated from matrices, and its retention
time was 5.2 min. No matrix effect was ob-
served around the retention time of apigenin,
confirming the good selectivity of the method.
Linearity (quantification capacity) was achieved
by plotting calibration curves of apigenin
within the ranges of 6.25 to 200 mg·mL
1
for chamomile and 0.078 to 2.5 mg·mL
1
for
parsley. For apigenin in chamomile, the cali-
bration data showed that the linear range
was6.25to200mg·mL
1
and could be de-
scribed by the linear regression equation y 5
5171x 50 (r
2
50.999). For apigenin in
parsley, the linear range extended from 0.078
to 2.5 mg·mL
1
with a regression equation of
y54610x 832 (r
2
50.997).
Apigenin accumulation. The Bodegold
and Zloty Lan chamomile cultivars produced
0.704 ± 0.173 and 0.733 ± 0.154 mg apigenin/g
dried tissue, respectively (Table 1 and Fig. 6).
Attest showed no significant difference in the
Table 1. Dried usable biomass, unusable biomass, and apigenin accumulation in cultivars of chamomile
(Matricaria recutita) and parsley (Petroselinum crispum) produced in an indoor deep-water culture
system. Inflorescences were the usable biomass for chamomile, with all vegetative tissue counted as
unusable biomass. For parsley, the leaves were considered usable and the stems were considered un-
usable biomass. Values are reported as the mean ± standard deviation.
Cultivar
Usable
biomass (g)
Unusable
biomass (g)
Apigenin concn
(mg·g
1
dried sample)
Total apigenin
(mg/plant)
M. recutita Bodegold 18.53 ± 20.79 183.87 ± 69.52 0.7036 ± 0.1726 15.32 ± 20.32
M. recutita Zloty Lan 4.39 ± 4.83 75.22 ± 39.25 0.7334 ± 0.1544 5.49 ± 4.11
P. crispum Darki 21.39 ± 5.11 8.04 ± 1.74 0.0250 ± 0.0463 0.58 ± 1.13
P. crispum Giant of Italy 49.30 ± 15.43 34.96 ± 15.88 0.0032 ± 0.0013 0.15 ± 0.07
P. crispum Wega 32.82 ± 11.38 14.12 ± 6.17 0.0050 ± 0.0050 0.16 ± 0.15
Fig. 3. The Bodegold and Zloty Lan chamomile
(Matricaria chamomilla) cultivars produced
18.5 ± 20.8 g and 4.3 ± 4.8 g of flowers per
plant, respectively. No statistically significant
difference in flower production was found be-
tween these two cultivars. Because apigenin
accumulates in the flowers of chamomile, the
vegetative tissue was considered unusable.
Fig. 4. Darki, Giant of Italy, and Wega parsley
(Petroselinum crispum) cultivars produced
21.4 ± 5.1 g, 49.3 ± 15.4 g, and 32.8 ± 11.4 g
of leaf tissue per plant, respectively. The
Giant of Italy cultivar produced significantly
more leaf tissue than that of the other culti-
vars [F(2) 512; P50.0003]. Because apige-
nin accumulates in the leaves of parsley, the
stem tissue was considered unusable.
HORTSCIENCE VOL. 60(1) JANUARY 2025 19
apigenin concentrations of the two cultivars.
The parsley cultivars accumulated lower con-
centrations of apigenin compared with that of
chamomile, with 0.025 ± 0.046, 0.003 ± 0.001,
and 0.005 ± 0.005 mg apigenin/g dried tissue
in the Darki, Giant of Italy, and Wega cultivars,
respectively (Table 1 and Fig. 7). However,
one plant from the Darki parsley cultivar was
an outlier, with 0.139 mg apigenin/g dried tis-
sue, which slightly skewed the average for this
cultivar. An ANOVA also showed no significant
difference in the apigenin concentrations among
the parsley cultivars, which was unexpected.
Previous research of celery and chrysanthe-
mum (Chrysanthemum ×morifolium) indicated
that apigenin production is cultivar-dependent
(Wang et al. 2018; Yan et al. 2014). Although
the present research did not find a cultivar de-
pendence for the trialed chamomile or parsley,
apigenin levels may differ in other cultivars.
The concentrations of apigenin in the
chamomile flowers and parsley leaves were
also unexpected. Previous research isolated
7.01 ± 0.07 mg apigenin/g of dried chamo-
mile flowers (Miguel et al. 2015) and 9.48 ±
0.11 mg apigenin/g of dried parsley leaves
(Poureini et al. 2022). The present study
found considerably lower levels of apigenin
accumulation in both herbs. One possible ex-
planation is that the indoor vertical farm with
a spectral output of 360 to 780 nm did not
have ultraviolet-B light. Previous studies have
found that ultraviolet irradiation increases produc-
tion of flavonoids through activity of the chal-
cone synthase enzyme, which catalyzes the first
step of the flavonoid biosynthetic pathway
(Schmelzer et al. 1988). In plants, apigenin
is a pigment that contributes to the color of
white and pale-yellow flowers (Iwashina
2015) and protects against damage by ultra-
violet-B radiation (Righini et al. 2019).
Therefore, the lack of ultraviolet light may
have reduced apigenin biosynthesis. Future
research should investigate whether the addi-
tion of ultraviolet-B light to indoor produc-
tion increases the accumulation of apigenin.
Because the parsley cultivars generated
more usable biomass and the chamomile cul-
tivars accumulated more apigenin in the us-
able tissue, the overall productivity of each
cultivar was ascertained by considering api-
genin production on a whole-plant basis. The
Bodegold and Zloty Lan chamomile cultivars
produced 15.32 ± 20.32 and 5.49 ± 4.11 mg
apigenin per plant (Table 1 and Fig. 8). In
parsley, the Darki, Giant of Italy, and Wega
cultivars produced 0.58 ± 1.13, 0.15 ± 0.07,
and 0.16 ± 0.15 mg apigenin per plant (Table 1
and Fig. 9). When considering the total us-
able biomass and concentration of apigenin
in the dried tissue, there was no significant
difference in overall apigenin production
between the chamomile cultivars or among
the parsley cultivars. However, because of
the higher concentration of apigenin in cham-
omile flowers compared with that in parsley
leaves, the chamomile cultivars generated more
Fig. 5. High-performance liquid chromatography (HPLC) chromatograms of apigenin from the standard
(A) and a sample from chamomile (B).
Fig. 6. In the inflorescences, the Bodegold and
Zloty Lan chamomile (Matricaria chamomilla)
cultivars produced 0.704 ± 0.173 and 0.733 ±
0.154 mg apigenin/g dried tissue, respectively,
with no significant difference in the apigenin
concentration between these two cultivars.
Fig. 7. The Darki, Giant of Italy, and Wega pars-
ley (Petroselinum crispum) cultivars accumu-
lated 0.025 ± 0.046, 0.003 ± 0.001, and 0.005 ±
0.005 mg apigenin/g dried leaf tissue, respec-
tively, with no significant difference in apigenin
accumulation among the cultivars.
Fig. 8. Total apigenin production per plant from
chamomile (Matricaria chamomilla)inflores-
cences. The Bodegold and Zloty Lan cultivars
produced 15.32 ± 20.32 and 5.49 ± 4.11 mg
apigenin per plant, respectively. No signifi-
cant difference in apigenin production was
found between cultivars.
20 HORTSCIENCE VOL. 60(1) JANUARY 2025
apigenin than that generated by the parsley cul-
tivars on a whole-plant basis.
Discussion
Although the chamomile cultivars pro-
duced more apigenin per plant compared to
that of parsley, other important considerations
are the time to maturity and labor of harvest.
Both parsley and chamomile can be harvested
multiple times throughout the growing pe-
riod. Under field conditions, parsley can be
harvested up to eight times, with dry matter
content increasing with successive harvests
(Alan et al. 2017). Field-grown chamomile is
frequently harvested up to four times. How-
ever, the efficiency of harvest is variable be-
cause the continually blooming plants have
inflorescences at different developmental stages
(Ghareeb et al. 2022). Previous research of
‘Bodegold’chamomile grown under field con-
ditions isolated 70 to 137 g·m
2
of dried flow-
ers in an 8-month growing season depending
on the planting density (Rahmati et al. 2011).
Based on spacing used in the present study, 24
‘Bodegold’chamomile plants could be grown
in a 1-m
2
footprint with 2 m of vertical growing
space. Because ‘Bodegold’yielded an average
of 18.5 g of dried flowers per plant, the expected
yield would be approximately 445 g·m
2
of
dried flowers in an indoor vertical farm. Further-
more, the time from transplant to final harvest
was80d,meaningitwouldbeeasilypossibleto
generate four crop cycles in a calendar year in a
controlled environment yielding approximately
1.78 kg·m
2
·year
1
of dried flowers. There-
fore, indoor vertical farming of ‘Bodegold’
chamomile is expected to produce significantly
greater yields compared with that of field pro-
duction because vertical farming uses space
more efficiently and indoor systems are not
season-dependent.
The Bodegold chamomile cultivar yielded
the greatest amount of apigenin per plant, with
an average of 15.3 mg, meaning it could be pos-
sible to isolate approximately 1.5 g·m
2
·year
1
of apigenin based on the plant spacing used
in this study. It is challenging to estimate the
profitability of growing chamomile as a bio-
pharmaceutical because the economic value
of apigenin is dependent on the source and
purity of the commercial product. Further-
more, it would be important to consider
factors such as the cost of inputs, labor,
and isolating apigenin to determine the
economic viability of selecting chamomile
as a biopharmaceutical.
In this study, chamomile was harvested
twice per week to collect inflorescences be-
fore the disc florets dehisced. It is essential to
harvest chamomile at the correct develop-
mental stage because fully opened buds have
a lower concentration of apigenin (Letchamo
1996). In this study, the number of flowers
increased over time as the plants matured, but
the time to collect the flowers also increased.
For commercial production of chamomile,
the labor associated with frequent hand-
harvesting would likely result in a signifi-
cant profit reduction compared with that
associated with the labor of harvesting parsley.
One possibility would be mechanizing the har-
vesting of the flowers, which is a common
method for field production. However, mechan-
ical harvesters have not yet been fully devel-
oped for indoor systems, and they would likely
need to be modified with lower tine spacing to
collect the unopened inflorescences. Future re-
search should also investigate whether apigenin
accumulation changes throughout multiple har-
vests to determine when the plants should be
replaced in the vertical farm.
Despite the higher yields of ‘Bodegold’,
one challenge identified in this study was the
high proportion of wasted biomass. A poten-
tial solution would be to harvest and repur-
pose the vegetative tissue at the end of the
growing period. Previous research found that
chamomile is a useful filler for rubber biocom-
posites. Chamomile biomass added to natural
rubber as 20% of the constituent material re-
sulted in a biocomposite with higher strength
than that of the base polymer and reduced
the use of synthetic materials (Masłowski
et al. 2021). Therefore, the vegetative by-
product of chamomile, which does not accu-
mulate high levels of apigenin, may be useful
for polymer technology.
Conclusion
Chamomile and parsley may be effective
crops for the biopharmaceutical production
of the anticancer compound apigenin. Both
herbs grow readily in a controlled environ-
ment with compact growth well-suited for
year-round indoor vertical farming. In this
study, both chamomile and parsley accumu-
lated apigenin, but the chamomile cultivars
produced more apigenin than that of any
parsley cultivar, yielding 0.704 ± 0.173 and
0.733 ± 0.154 mg apigenin/g dried flowers
in the Bodegold and Zloty Lan cultivars,
respectively. However, the observed yields
were lower than expected. Future research
should investigate the impact of adding ultra-
violet-B light to the indoor system on overall
apigenin accumulation. Despite the greater
yield of apigenin in chamomile compared
with that in parsley, regularly harvesting the
unopened inflorescences is more labor-inten-
sive than harvesting mature parsley leaves,
which may reduce the profitability of select-
ing chamomile as a biopharmaceutical crop.
Therefore, future research should also investi-
gate the profitability of isolating apigenin from
chamomile and consider novel applications of
the unharvestable biomass.
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